Adaptive algorithms for identifying large flows in IP traffic
Chabchoub, Yousra; Guillemin, Fabrice; Robert, Philippe
2009-01-01
We develop in this paper an adaptive algorithm based on Bloom filters in order to identify large flows. While most algorithms proposed so far in the technical literature rely on a periodic erasure of the Bloom filter, we propose in this paper to progressively decrement the various counters of the filter according to some overload criteria. When tested against real traffic traces, the proposed algorithm performs well in the sense that a high percentage of large flows in traffic are detected by the algorithm. In order to improve the accuracy of the algorithm, we introduce a shadow Bloom filter, which is less frequently decremented so that elephants have more chance of being identified. Since elephant detection issue is very close to flood attack detection, we adapt the proposed algorithm in order to detect SYN and volume flood attack in Internet traffic. The attack detection algorithm is tested against traffic traces from France Telecom collect and transit networks. Some performance issues are finally discussed...
Klunder, G.; Li, M.; Minderhoud, M.
2009-01-01
In 2006 in the Netherlands, a field operational test was carried out to study the effect of adaptive cruise control (ACC) and lane departure warning on driver behavior and traffic flow in real traffic. To estimate the effect for larger penetration rates, simulations were needed. For a reliable impac
TRANSIMS traffic flow characteristics
Nagel, K; Pieck, M; Donnelly, R; Barrett, C L; Nagel, Kai; Stretz, Paula; Pieck, Martin; Donnelly, Rick; Barrett, Christopher L.
1997-01-01
Knowledge of fundamental traffic flow characteristics of traffic simulation models is an essential requirement when using these models for the planning, design, and operation of transportation systems. In this paper we discuss the following: a description of how features relevant to traffic flow are currently under implementation in the TRANSIMS microsimulation, a proposition for standardized traffic flow tests for traffic simulation models, and the results of these tests for two different versions of the TRANSIMS microsimulation.
Effect of adaptive cruise control systems on mixed traffic flow near an on-ramp
Davis, L. C.
2007-06-01
Mixed traffic flow consisting of vehicles equipped with adaptive cruise control (ACC) and manually driven vehicles is analyzed using car-following simulations. Simulations of merging from an on-ramp onto a freeway reported in the literature have not thus far demonstrated a substantial positive impact of ACC. In this paper cooperative merging for ACC vehicles is proposed to improve throughput and increase distance traveled in a fixed time. In such a system an ACC vehicle senses not only the preceding vehicle in the same lane but also the vehicle immediately in front in the other lane. Prior to reaching the merge region, the ACC vehicle adjusts its velocity to ensure that a safe gap for merging is obtained. If on-ramp demand is moderate, cooperative merging produces significant improvement in throughput (20%) and increases up to 3.6 km in distance traveled in 600 s for 50% ACC mixed flow relative to the flow of all-manual vehicles. For large demand, it is shown that autonomous merging with cooperation in the flow of all ACC vehicles leads to throughput limited only by the downstream capacity, which is determined by speed limit and headway time.
Davis, L C
2015-01-01
Wirelessly connected vehicles that exchange information about traffic conditions can reduce delays caused by congestion. At a 2-to-1 lane reduction, the improvement in flow past a bottleneck due to traffic with a random mixture of 40% connected vehicles is found to be 52%. Control is based on connected-vehicle-reported velocities near the bottleneck. In response to indications of congestion the connected vehicles, which are also adaptive cruise control vehicles, reduce their speed in slowdown regions. Early lane changes of manually driven vehicles from the terminated lane to the continuous lane are induced by the slowing connected vehicles. Self-organized congestion at the bottleneck is thus delayed or eliminated, depending upon the incoming flow magnitude. For the large majority of vehicles, travel times past the bottleneck are substantially reduced. Control is responsible for delaying the onset of congestion as the incoming flow increases. Adaptive cruise control increases the flow out of the congested stat...
Synchronized flow in oversaturated city traffic.
Kerner, Boris S; Klenov, Sergey L; Hermanns, Gerhard; Hemmerle, Peter; Rehborn, Hubert; Schreckenberg, Michael
2013-11-01
Based on numerical simulations with a stochastic three-phase traffic flow model, we reveal that moving queues (moving jams) in oversaturated city traffic dissolve at some distance upstream of the traffic signal while transforming into synchronized flow. It is found that, as in highway traffic [Kerner, Phys. Rev. E 85, 036110 (2012)], such a jam-absorption effect in city traffic is explained by a strong driver's speed adaptation: Time headways (space gaps) between vehicles increase upstream of a moving queue (moving jam), resulting in moving queue dissolution. It turns out that at given traffic signal parameters, the stronger the speed adaptation effect, the shorter the mean distance between the signal location and the road location at which moving queues dissolve fully and oversaturated traffic consists of synchronized flow only. A comparison of the synchronized flow in city traffic found in this Brief Report with synchronized flow in highway traffic is made.
Effect of adaptive cruise control systems on mixed traffic flow near an on-ramp
Davis, L C
2005-01-01
Mixed traffic flow consisting of vehicles equipped with adaptive cruise control (ACC) and manually driven vehicles is analyzed using car-following simulations. Unlike simulations that show suppression of jams due to increased string stability, simulations of merging from an on-ramp onto a freeway have not thus far demonstrated a substantial positive impact of ACC. In this paper cooperative merging is proposed to increase throughput and increase distance traveled in a fixed time (reduce travel times). In such a system an ACC vehicle senses not only the preceding vehicle in the same lane but also the vehicle immediately in front in the opposite lane. Prior to reaching the merge region, the ACC vehicle adjusts its velocity to ensure that a safe gap for merging is obtained. If on-ramp demand is moderate, partial implementation of cooperative merging where only main line ACC vehicles react to an on-ramp vehicle is effective. Significant improvement in throughput (18%) and increases up to 3 km in distance traveled ...
Online traffic flow model applying dynamic flow-density relation
Kim, Y
2002-01-01
This dissertation describes a new approach of the online traffic flow modelling based on the hydrodynamic traffic flow model and an online process to adapt the flow-density relation dynamically. The new modelling approach was tested based on the real traffic situations in various homogeneous motorway sections and a motorway section with ramps and gave encouraging simulation results. This work is composed of two parts: first the analysis of traffic flow characteristics and second the development of a new online traffic flow model applying these characteristics. For homogeneous motorway sections traffic flow is classified into six different traffic states with different characteristics. Delimitation criteria were developed to separate these states. The hysteresis phenomena were analysed during the transitions between these traffic states. The traffic states and the transitions are represented on a states diagram with the flow axis and the density axis. For motorway sections with ramps the complicated traffic fl...
Directory of Open Access Journals (Sweden)
Tsz Leung Yip
2013-03-01
Full Text Available A model is developed for studying marine traffic flow through classical traffic flow theories, which can provide us with a better understanding of the phenomenon of traffic flow of ships. On one hand, marine traffic has its special features and is fundamentally different from highway, air and pedestrian traffic. The existing traffic models cannot be simply extended to marine traffic without addressing marine traffic features. On the other hand, existing literature on marine traffic focuses on one ship or two ships but does not address the issues in marine traffic flow.
Davis, L. C.
2016-06-01
Wirelessly connected vehicles that exchange information about traffic conditions can reduce delays caused by congestion. At a 2-to-1 lane reduction, the improvement in flow past a bottleneck due to traffic with a random mixture of 40% connected vehicles is found to be 52%. Control is based on connected-vehicle-reported velocities near the bottleneck. In response to indications of congestion the connected vehicles, which are also adaptive cruise control vehicles, reduce their speed in slowdown regions. Early lane changes of manually driven vehicles from the terminated lane to the continuous lane are induced by the slowing connected vehicles. Self-organized congestion at the bottleneck is thus delayed or eliminated, depending upon the incoming flow magnitude. For the large majority of vehicles, travel times past the bottleneck are substantially reduced. Control is responsible for delaying the onset of congestion as the incoming flow increases. Adaptive cruise control increases the flow out of the congested state at the bottleneck. The nature of the congested state, when it occurs, appears to be similar under a variety of conditions. Typically 80-100 vehicles are approximately equally distributed between the lanes in the 500 m region prior to the end of the terminated lane. Without the adaptive cruise control capability, connected vehicles can delay the onset of congestion but do not increase the asymptotic flow past the bottleneck. Calculations are done using the Kerner-Klenov three-phase theory, stochastic discrete-time model for manual vehicles. The dynamics of the connected vehicles is given by a conventional adaptive cruise control algorithm plus commanded deceleration. Because time in the model for manual vehicles is discrete (one-second intervals), it is assumed that the acceleration of any vehicle immediately in front of a connected vehicle is constant during the time interval, thereby preserving the computational simplicity and speed of a discrete-time model.
Ganu, Hrishikesh V
2008-01-01
Air Traffic Flow Management is the regulation of air traffic in order to avoid exceeding airport or flight sector capacity in handling traffic, and to ensure that available capacity is used efficiently. We have tried to explore the logic behind the claims by Bertsimas et.al about integral solutions to the LP relaxation of the Traffic Flow Management Problem(TFMP). Polyhedral theory only indicates that the stronger TFMP formulation of Bertsimas et.al might lead to integral solutions in some cases. Our computations indicate that the encouraging results reported by Bertsimas et.al are not merely fortuitous or due to their specific data set. Indeed, we found that the TFMP had integral solutions even in case of artificial data sets generated to include severe conflicts in the flight schedules. In our limited tests with 4-5 scenarios, we obtained non-integral solutions only once. This is of significant practical importance because, the LP relaxation can be solved even on small machines with low memory and processor...
Synchronized flow in oversaturated city traffic
Kerner, Boris S.; Klenov, Sergey L.; Hermanns, Gerhard; Hemmerle, Peter; Rehborn, Hubert; Schreckenberg, Michael
2013-11-01
Based on numerical simulations with a stochastic three-phase traffic flow model, we reveal that moving queues (moving jams) in oversaturated city traffic dissolve at some distance upstream of the traffic signal while transforming into synchronized flow. It is found that, as in highway traffic [Kerner, Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.036110 85, 036110 (2012)], such a jam-absorption effect in city traffic is explained by a strong driver's speed adaptation: Time headways (space gaps) between vehicles increase upstream of a moving queue (moving jam), resulting in moving queue dissolution. It turns out that at given traffic signal parameters, the stronger the speed adaptation effect, the shorter the mean distance between the signal location and the road location at which moving queues dissolve fully and oversaturated traffic consists of synchronized flow only. A comparison of the synchronized flow in city traffic found in this Brief Report with synchronized flow in highway traffic is made.
Directory of Open Access Journals (Sweden)
He Huang
2013-01-01
Full Text Available Forecasting of urban traffic flow is important to intelligent transportation system (ITS developments and implementations. The precise forecasting of traffic flow will be pretty helpful to relax road traffic congestion. The accuracy of traditional single model without correction mechanism is poor. Summarizing the existing prediction models and considering the characteristics of the traffic itself, a traffic flow prediction model based on fuzzy c-mean clustering method (FCM and advanced neural network (NN was proposed. FCM can improve the prediction accuracy and robustness of the model, while advanced NN can optimize the generalization ability of the model. Besides these, the output value of the model is calibrated by the correction mechanism. The experimental results show that the proposed method has better prediction accuracy and robustness than the other models.
Probabilistic description of traffic flow
Mahnke, R.; Kaupužs, J.; Lubashevsky, I.
2005-03-01
A stochastic description of traffic flow, called probabilistic traffic flow theory, is developed. The general master equation is applied to relatively simple models to describe the formation and dissolution of traffic congestions. Our approach is mainly based on spatially homogeneous systems like periodically closed circular rings without on- and off-ramps. We consider a stochastic one-step process of growth or shrinkage of a car cluster (jam). As generalization we discuss the coexistence of several car clusters of different sizes. The basic problem is to find a physically motivated ansatz for the transition rates of the attachment and detachment of individual cars to a car cluster consistent with the empirical observations in real traffic. The emphasis is put on the analogy with first-order phase transitions and nucleation phenomena in physical systems like supersaturated vapour. The results are summarized in the flux-density relation, the so-called fundamental diagram of traffic flow, and compared with empirical data. Different regimes of traffic flow are discussed: free flow, congested mode as stop-and-go regime, and heavy viscous traffic. The traffic breakdown is studied based on the master equation as well as the Fokker-Planck approximation to calculate mean first passage times or escape rates. Generalizations are developed to allow for on-ramp effects. The calculated flux-density relation and characteristic breakdown times coincide with empirical data measured on highways. Finally, a brief summary of the stochastic cellular automata approach is given.
Adaptive Traffic Control Systems in a medium-sized Scandinavian city
DEFF Research Database (Denmark)
Agerholm, Niels; Olesen, Anne Vingaard
2017-01-01
Adaptive Traffic Control Systems (ATCS) are aimed at reducing congestion. ATCS adapt to approaching traffic to continuously optimise the traffic flows in question. ATCS have been implemented in many locations, including the Scandinavian countries, with various effects. Due to congestion problems...
Empirical analysis of heterogeneous traffic flow
Ambarwati, L.; Pel, A.J.; Verhaeghe, R.J.; Van Arem, B.
2013-01-01
Traffic flow in many developing countries is strongly mixed comprising vehicle types, such as motorcycles, cars, (mini) buses, and trucks; furthermore, traffic flow typically exhibits free inter-lane exchanges. This phenomenon causes a complex vehicle interaction, rendering most existing traffic flo
Characteristics of synchronized traffic in mixed traffic flow
Institute of Scientific and Technical Information of China (English)
Ning Hong-Xin; Xue Yu
2012-01-01
In this paper,the characteristics of synchronized traffic in mixed traffic flow are investigated based on the braking light model.By introducing the energy dissipation and the distribution of slowdown vehicles,the effects of the maximum velocity,the mixing ratio,and the length of vehicles on the synchronized flow are discussed.It is found that the maximum velocity plays a great role in the synchronized flow in mixed traffic.The energy dissipation and the distribution of slowdown vehicles in the synchronized flow region are greatly different from those in free flow and a traffic jamming region.When all of vehicles have the same maximum velocity with Vmax ＞ 15,the mixed traffic significantly displays synchronized flow,which has been demonstrated by the relation between flow rate and occupancy and estimation of the cross-correlation function.Moreover,the energy dissipation in the synchronized flow region does not increase with occupancy.The distribution of slowdown vehicles shows a changeless platform in the synchronized flow region.This is an interesting phenomenon. It helps to deeply understand the synchronized flow and greatly reduce the energy dissipation of traffic flow.
Robust Traffic Flow Management: Coevolutionary Approach Project
National Aeronautics and Space Administration — We will develop a Coevolutionary Decision Support Tool (CDST) that explicitly incorporates weather uncertainty (non-probabilistically) into strategic Traffic Flow...
Traffic flow wide-area surveillance system definition
Energy Technology Data Exchange (ETDEWEB)
Allgood, G.O.; Ferrell, R.K.; Kercel, S.W.; Abston, R.A.; Carnal, C.L. [Oak Ridge National Lab., TN (United States); Moynihan, P.I. [Jet Propulsion Lab., Pasadena, CA (United States)
1994-11-01
Traffic Flow Wide-Area Surveillance (TFWAS) is a system for assessing the state of traffic flow over a wide area for enhanced traffic control and improved traffic management and planning. The primary purpose of a TFWAS system is to provide a detailed traffic flow description and context description to sophisticated traffic management and control systems being developed or envisioned for the future. A successful TFWAS system must possess the attributes of safety, reconfigurability, reliability, and expandability. The primary safety premise of TFWAS is to ensure that no action or failure of the TFWAS system or its components can result in risk of injury to humans. A wide variety of communication techniques is available for use with TFWAS systems. These communication techniques can be broken down into two categories, landlines and wireless. Currently used and possible future traffic sensing technologies have been examined. Important criteria for selecting TFWAS sensors include sensor capabilities, costs, operational constraints, sensor compatibility with the infrastructure, and extent. TFWAS is a concept that can take advantage of the strengths of different traffic sensing technologies, can readily adapt to newly developed technologies, and can grow with the development of new traffic control strategies. By developing innovative algorithms that will take information from a variety of sensor types and develop descriptions of traffic flows over a wide area, a more comprehensive understanding of the traffic state can be provided to the control system to perform the most reasonable control actions over the entire wide area. The capability of characterizing the state of traffic over an entire region should revolutionize developments in traffic control strategies.
Traffic Flow Management Wrap-Up
Grabbe, Shon
2011-01-01
Traffic Flow Management involves the scheduling and routing of air traffic subject to airport and airspace capacity constraints, and the efficient use of available airspace. Significant challenges in this area include: (1) weather integration and forecasting, (2) accounting for user preferences in the Traffic Flow Management decision making process, and (3) understanding and mitigating the environmental impacts of air traffic on the environment. To address these challenges, researchers in the Traffic Flow Management area are developing modeling, simulation and optimization techniques to route and schedule air traffic flights and flows while accommodating user preferences, accounting for system uncertainties and considering the environmental impacts of aviation. This presentation will highlight some of the major challenges facing researchers in this domain, while also showcasing recent innovations designed to address these challenges.
Empirical synchronized flow in oversaturated city traffic
Kerner, Boris S.; Hemmerle, Peter; Koller, Micha; Hermanns, Gerhard; Klenov, Sergey L.; Rehborn, Hubert; Schreckenberg, Michael
2014-09-01
Based on a study of anonymized GPS probe vehicle traces measured by personal navigation devices in vehicles randomly distributed in city traffic, empirical synchronized flow in oversaturated city traffic has been revealed. It turns out that real oversaturated city traffic resulting from speed breakdown in a city in most cases can be considered random spatiotemporal alternations between sequences of moving queues and synchronized flow patterns in which the moving queues do not occur.
Yuan, Yao-Ming; Jiang, Rui; Hu, Mao-Bin; Wu, Qing-Song; Wang, Ruili
2009-06-01
In this paper, we have investigated traffic flow characteristics in a traffic system consisting of a mixture of adaptive cruise control (ACC) vehicles and manual-controlled (manual) vehicles, by using a hybrid modelling approach. In the hybrid approach, (i) the manual vehicles are described by a cellular automaton (CA) model, which can reproduce different traffic states (i.e., free flow, synchronised flow, and jam) as well as probabilistic traffic breakdown phenomena; (ii) the ACC vehicles are simulated by using a car-following model, which removes artificial velocity fluctuations due to intrinsic randomisation in the CA model. We have studied the traffic breakdown probability from free flow to congested flow, the phase transition probability from synchronised flow to jam in the mixed traffic system. The results are compared with that, where both ACC vehicles and manual vehicles are simulated by CA models. The qualitative and quantitative differences are indicated.
Chevoir, François; Gondret, Philippe; Lassarre, Sylvain; Lebacque, Jean-Patrick; Schreckenberg, Michael
2009-01-01
This book covers several research fields, all of which deal with transport. Three main topics are treated: road traffic, granular matter, and biological transport. Different points of view, i.e. modelling, simulations, experiments, and phenomenological observations, are considered. Sub-topics include: highway or urban vehicular traffic (dynamics of traffic, macro/micro modelling, measurements, data analysis, security issues, psychological issues), pedestrian traffic, animal traffic (e.g. social insects), collective motion in biological systems (molecular motors...), granular flow (dense flows, intermittent flows, solid/liquid transition, jamming, force networks, fluid and solid friction), networks (biological networks, urban traffic, the internet, vulnerability of networks, optimal transport networks) and cellular automata applied to the various aforementioned fields.
11th Traffic and Granular Flow Conference
Daamen, Winnie
2016-01-01
The Conference on Traffic and Granular Flow brings together international researchers from different fields ranging from physics to computer science and engineering to discuss the latest developments in traffic-related systems. Originally conceived to facilitate new ideas by considering the similarities of traffic and granular flow, TGF'15, organised by Delft University of Technology, now covers a broad range of topics related to driven particle and transport systems. Besides the classical topics of granular flow and highway traffic, its scope includes data transport (Internet traffic), pedestrian and evacuation dynamics, intercellular transport, swarm behaviour and the collective dynamics of other biological systems. Recent advances in modelling, computer simulation and phenomenology are presented, and prospects for applications, for example to traffic control, are discussed. The conference explores the interrelations between the above-mentioned fields and offers the opportunity to stimulate interdisciplinar...
Traffic Flow Characteristics with Transportation Plans Components
Directory of Open Access Journals (Sweden)
Hrvoje Baričević
2012-10-01
Full Text Available Knowledge of traffic characteristics is useful to the highwayengineer in developing highway and transportation plans, performingeconomic analyses, establishing geometric design criteria,selecting and implementing traffic control measures, andevaluating the pe1[ormance of transportation facilities. Doze/ISof measures have been employed to describe the quality andquantity of traffic flow. This paper presents information onthose flow characteristics that fundamentally bear on the planning,design, and operation of highway and transport facilities:traffic speed, travel time, volume, and density.
Bayesian Particle Tracking of Traffic Flows
2014-01-01
We develop a Bayesian particle filter for tracking traffic flows that is capable of capturing non-linearities and discontinuities present in flow dynamics. Our model includes a hidden state variable that captures sudden regime shifts between traffic free flow, breakdown and recovery. We develop an efficient particle learning algorithm for real time on-line inference of states and parameters. This requires a two step approach, first, resampling the current particles, with a mixture predictive ...
Luding, Stefan; Bovy, Piet; Schreckenberg, Michael; Wolf, Dietrich
2005-01-01
These proceedings are the fifth in the series Traffic and Granular Flow, and we hope they will be as useful a reference as their predecessors. Both the realistic modelling of granular media and traffic flow present important challenges at the borderline between physics and engineering, and enormous progress has been made since 1995, when this series started. Still the research on these topics is thriving, so that this book again contains many new results. Some highlights addressed at this conference were the influence of long range electric and magnetic forces and ambient fluids on granular media, new precise traffic measurements, and experiments on the complex decision making of drivers. No doubt the “hot topics” addressed in granular matter research have diverged from those in traffic since the days when the obvious analogies between traffic jams on highways and dissipative clustering in granular flow intrigued both c- munities alike. However, now just this diversity became a stimulating feature of the ...
SIMPLE LATTICE BOLTZMANN MODEL FOR TRAFFIC FLOWS
Institute of Scientific and Technical Information of China (English)
Yan Guangwu; Hu Shouxin
2000-01-01
A lattice Boltzmann model with 5-bit lattice for traffic flows is proposed.Using the Chapman-Enskog expansion and multi-scale technique,we obtain the higher-order moments of equilibrium distribution function.A simple traffic light problem is simulated by using the present lattice Boltzmann model,and the result agrees well with analytical solution.
Traffic Flow Density Distribution Based on FEM
Ma, Jing; Cui, Jianming
In analysis of normal traffic flow, it usually uses the static or dynamic model to numerical analyze based on fluid mechanics. However, in such handling process, the problem of massive modeling and data handling exist, and the accuracy is not high. Finite Element Method (FEM) is a production which is developed from the combination of a modern mathematics, mathematics and computer technology, and it has been widely applied in various domain such as engineering. Based on existing theory of traffic flow, ITS and the development of FEM, a simulation theory of the FEM that solves the problems existing in traffic flow is put forward. Based on this theory, using the existing Finite Element Analysis (FEA) software, the traffic flow is simulated analyzed with fluid mechanics and the dynamics. Massive data processing problem of manually modeling and numerical analysis is solved, and the authenticity of simulation is enhanced.
Traffic flow dynamics data, models and simulation
Treiber, Martin
2013-01-01
This textbook provides a comprehensive and instructive coverage of vehicular traffic flow dynamics and modeling. It makes this fascinating interdisciplinary topic, which to date was only documented in parts by specialized monographs, accessible to a broad readership. Numerous figures and problems with solutions help the reader to quickly understand and practice the presented concepts. This book is targeted at students of physics and traffic engineering and, more generally, also at students and professionals in computer science, mathematics, and interdisciplinary topics. It also offers material for project work in programming and simulation at college and university level. The main part, after presenting different categories of traffic data, is devoted to a mathematical description of the dynamics of traffic flow, covering macroscopic models which describe traffic in terms of density, as well as microscopic many-particle models in which each particle corresponds to a vehicle and its driver. Focus chapters on ...
International Workshop on Traffic and Granular Flow
Herrmann, Hans; Schreckenberg, Michael; Wolf, Dietrich; Social, Traffic and Granular Dynamics
2000-01-01
"Are there common phenomena and laws in the dynamic behavior of granular materials, traffic, and socio-economic systems?" The answers given at the international workshop "Traffic and Granular Flow '99" are presented in this volume. From a physical standpoint, all these systems can be treated as (self)-driven many-particle systems with strong fluctuations, showing multistability, phase transitions, non-linear waves, etc. The great interest in these systems is due to several unexpected new discoveries and their practical relevance for solving some fundamental problems of today's societies. This includes intelligent measures for traffic flow optimization and methods from "econophysics" for stabilizing (stock) markets.
Buslaev, Alexander; Bugaev, Alexander; Yashina, Marina; Schadschneider, Andreas; Schreckenberg, Michael; TGF11
2013-01-01
This book continues the biannual series of conference proceedings, which has become a classical reference resource in traffic and granular research alike. It addresses new developments at the interface between physics, engineering and computational science. Complex systems, where many simple agents, be they vehicles or particles, give rise to surprising and fascinating phenomena. The contributions collected in these proceedings cover several research fields, all of which deal with transport. Topics include highway, pedestrian and internet traffic, granular matter, biological transport, transport networks, data acquisition, data analysis and technological applications. Different perspectives, i.e. modeling, simulations, experiments and phenomenological observations, are considered.
Fastlane: Traffic flow modeling and multi-class dynamic traffic management
Schreiter, T.; Van Wageningen-Kessels, F.L.M.; Yuan, Y.; Van Lint, J.W.C.; Hoogendoorn, S.P.
2012-01-01
Dynamic Traffic Management (DTM) aims to improve traffic conditions. DTM usually consists of two steps: first the current traffic is estimated, then appropriate control actions are determined based on that estimate. In order to estimate and control the traffic, a suitable traffic flow model that rep
Visualization, Selection, and Analysis of Traffic Flows.
Scheepens, Roeland; Hurter, Christophe; van de Wetering, Huub; van Wijk, Jarke J
2016-01-01
Visualization of the trajectories of moving objects leads to dense and cluttered images, which hinders exploration and understanding. It also hinders adding additional visual information, such as direction, and makes it difficult to interactively extract traffic flows, i.e., subsets of trajectories. In this paper we present our approach to visualize traffic flows and provide interaction tools to support their exploration. We show an overview of the traffic using a density map. The directions of traffic flows are visualized using a particle system on top of the density map. The user can extract traffic flows using a novel selection widget that allows for the intuitive selection of an area, and filtering on a range of directions and any additional attributes. Using simple, visual set expressions, the user can construct more complicated selections. The dynamic behaviors of selected flows may then be shown in annotation windows in which they can be interactively explored and compared. We validate our approach through use cases where we explore and analyze the temporal behavior of aircraft and vessel trajectories, e.g., landing and takeoff sequences, or the evolution of flight route density. The aircraft use cases have been developed and validated in collaboration with domain experts.
Cellular automata models for synchronized traffic flow
Jiang Rui
2003-01-01
This paper presents a new cellular automata model for describing synchronized traffic flow. The fundamental diagrams, the spacetime plots and the 1 min average data have been analysed in detail. It is shown that the model can describe the outflow from the jams, the light synchronized flow as well as heavy synchronized flow with average speed greater than approximately 24 km h sup - sup 1. As for the synchronized flow with speed lower than 24 km h sup - sup 1 , it is unstable and will evolve into the coexistence of jams, free flow and light synchronized flow. This is consistent with the empirical findings (Kerner B S 1998 Phys. Rev. Lett. 81 3797).
A speed-flow relationship model of highway traffic flow
Institute of Scientific and Technical Information of China (English)
WANG Wei; LI Wei; REN Gang
2005-01-01
In the view that the generally used speed-flow relationship model is insufficient in the traffic analysis under over-saturated conditions, this paper first establishes the theoretical models of speed flow relationship for each highway class based upon a large number of traffic data collected from the field. Then by analyzing the traffic flow dissipation mechanism under peak hour over-saturated traffic conditions, the speed flow relationship model structures for each highway class are reviewed under different traffic load conditions. Through curve-fitting of large numbers of observed data, functional equations of general speed-flow relationship models for each highway class under any traffic load conditions are established. The practical model parameters for each highway class under different design speeds are also put forward. This model is successful in solving the speed-forecasting problem of the traffic flow under peak hour over-saturated conditions. This provides the theoretical bases for the development of projects related to highway network planning, economic analysis, etc.
A new dynamics model for traffic flow
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
As a study method of traffic flow, dynamics models were developedand applied in the last few decades. However, there exist some flaws in most existing models. In this note, a new dynamics model is proposed by using car-following theory and the usual connection method of micro-macro variables, which can overcome some ubiquitous problems in the existing models. Numerical results show that the new model can very well simulate traffic flow conditions, such as congestion, evacuation of congestion, stop-and-go phenomena and phantom jam.
Institute of Scientific and Technical Information of China (English)
王晓原; 张敬磊; 马立云
2014-01-01
研究交通流演化规律对交通安全措施的实施具有重要意义。交通流的演化过程一般可分为交通流的量变与质变。鉴于交通自由流状态、拥挤流状态及间歇流状态的分布均可由伽马分布表达，利用伽马分布及其变点检验算法进行变点搜索及检验，确定变点前后的交通流状态。结合柯尔莫哥洛夫-斯米尔诺夫检验方法对观测数据是否服从伽马分布进行拟合优度检验。为较直观说明交通流的演化规律，结合极大似然估计，给出了适应交通流演化的伽马分布形状参数估计。实验结果表明，伽马分布形状参数估计的研究是探索交通流演化规律的有利途径。%It is significant to research traffic flow evolvement for the traffic safety implementation. The evolution process of traffic flow is generally classified as quantitative change and qualitative change. Distributions of free, congested and intermittent flow all can be replaced by gamma distribution. So, in this paper, the traffic flow states before and after change-point are confirmed by searching and testing change-point with gamma distribution and change-point testing method. Kolmogorov-Smirnov test method is used to test whether or not the observation data is in line with gamma distribution. Gamma distribution shape parameter adapting to traffic flow evolvement is estimated with maximum likely estimation method in order to explain evolvement directly. The experimental results indicate that studying gamma distribution shape parameter is a favorable way to research traffic flow evolvement.
Effect of Adaptive Delivery Capacity on Networked Traffic Dynamics
Institute of Scientific and Technical Information of China (English)
CAO Xian-Bin; DU Wen-Bo; CHEN Cai-Long; ZHANG Jun
2011-01-01
@@ We introduce an adaptive delivering capacity mechanism into the traffic dynamic model on scale-free networks under shortest path routing strategy and focus on its effect on the network capacity measured by the critical point(Rc) of phase transition from free flow to congestion.Under this mechanism,the total node's delivering capacity is fixed and the allocation of delivering capacity on node i is proportional to niφ,where ni is the queue length of node i and φ is the adjustable parameter.It is found that the network capacity monotonously increases with the increment of φ,but there exists an optimal value of parameter φ leading to the highest transportation efficiency measured by average travelling time(〈T〉).Our work may be helpful for optimal design of networked traffic dynamics.%We introduce an adaptive delivering capacity mechanism into the traffic dynamic model on scale-free networks under shortest path routing strategy and focus on its effect on the network capacity measured by the critical point (Rc) of phase transition from free flow to congestion.Under this mechanism, the total node's delivering capacity is fixed and the allocation of delivering capacity on node i is proportional to niφ, where ni is the queue length of node i and φ is the adjustable parameter.It is found that the network capacity monotonously increases with the increment of φ, but there exists an optimal value of parameter φ leading to the highest transportation efficiency measured by average travelling time (＜T＞).Our work may be helpful for optimal design of networked traffic dynamics.
Microstructure and microdynamics of uninterrupted traffic flow
Gavrilov, Konstantin L.
1997-10-01
In this paper, ``uninterrupted homogeneous traffic flow'' is viewed as a dynamic system of spontaneously aggregating and breaking clusters of cars. This approach gives qualitative and quantitative descriptions of density fluctuations and dynamics of free traffic flow in terms of car clusters, and their distributions with respect to the number of cars in a cluster. The distributions have a nontrivial shape and a nonlinear dependence on the density of cars on the expressway. Their shape and evolution as a function of car density are described adequately by a model proposed here. This one-parameter model based on a modified Smoluchowski equation predicts a critical density at which a phase transition occurs from free to synchronized traffic flow for a multilane expressway: ρcr=16+/-3 vehicles km-1 (lane)-1, and that below this critical density traffic flow can be treated as a one-dimensional system. The model may also find application in the study of the low density pneumatic transport of granular and powdered materials.
Traffic Flow Control In Automated Highway Systems
Alvarez, Luis; Horowitz, Roberto
1997-01-01
This report studies the problem of traffic control in the Automated Highway System (AHS) hierarchical architecture of the California PATH program. A link layer controller for the PATH AHS architecture is presented. It is shown that the proposed control laws stabilize the vehicular density and flow around predetermined profiles.
Development of kink jams in traffic flow
Kurtze, Douglas
Near the threshold of absolute stability of uniform, steady traffic flow, car-following models can often be reduced to a modified Korteweg-deVries (mKdV) equation plus small corrections. The mKdV equation has a continuous family of hyperbolic-kink solutions describing boundaries between regions of different traffic densities, i.e. the edges of traffic jams. A solvability calculation picks out the one member of this family which is consistent with the correction terms; this is usually labelled the ``selected'' kink. This identification is problematic, however, since it must be the downstream boundary condition that determines which kink solution is realized. We display a two-parameter family of mKdV solutions which has the kink solutions as one limit and uniform flow as another, and show how the correction terms can lead to kinks developing from initially near-uniform traffic. We then clarify the meaning of the usual solvability calcuation and of the ``selected'' kink.
Adaptive Queue Management with Restraint on Non-Responsive Flows
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Lan Li
2003-12-01
Full Text Available This paper proposes an adaptive queue management scheme (adaptive RED to improve Random Early Detection (RED on restraining non-responsive flows. Due to a lack of flow control mechanism, non-responsive flows can starve responsive flows for buffer and bandwidth at the gateway. In order to solve the disproportionate resource problem, RED framework is modified in this way: on detecting when the non-responsive flows starve the queue, packet-drop intensity (Max_p in RED can be adaptively adjusted to curb non-responsive flows for resource fair-sharing, such as buffer and bandwidth fair-sharing. Based on detection of traffic behaviors, intentionally restraining nonresponsive flows is to increase the throughput and decrease the drop rate of responsive flows. Our experimental results based on adaptive RED shows that the enhancement of responsive traffic and the better sharing of buffer and bandwidth can be achieved under a variety of traffic scenarios.
Anacleto, Osvaldo; Queen, Catriona; Albers, Casper J.
2013-01-01
Traffic flow data are routinely collected for many networks worldwide. These invariably large data sets can be used as part of a traffic management system, for which good traffic flow forecasting models are crucial. The linear multiregression dynamic model (LMDM) has been shown to be promising for f
Economic Analysis of Traffic Flow with an Evolution Equation
Institute of Scientific and Technical Information of China (English)
冯苏苇
2005-01-01
Based on two main hypotheses of traffic economical equilibrium and the relationship between traffic density and the demand, an evolution equation of traffic cost was proposed to describe the change of cost under decreasing toll. Economical explanation of the model and a numerical case were given to demonstrate the constraint between the marginal traffic demand and the flow velocity.
Noise-Induced Phase Transition in Traffic Flow
Institute of Scientific and Technical Information of China (English)
LIKe-Ping; GAOZi-You
2004-01-01
One of the dynamic phases of the traffic flow is the traffic jam. It appears in traffic flow when the vehicle density is larger than the critical value. In this paper, a new method is presented to investigate the traffic jam when the vehicle density is smaller than the critical value. In our method, we introduce noise into the traffic system after sufficient transient time. Under the effect of noise, the traffic jam appears, and the phase transition from free to synchronized flow occurs in traffic flow. Our method is tested for the deterministic NaSch traffic model. The simulation results demonstrate that there exist a broad range of lower densities at which the noise effect leading to traffic jam can be observed.
Chaos control in traffic flow models
Shahverdiev, E M; Shahverdiev, Elman Mohammed; Tadaki, Shin-ichi
1998-01-01
Chaos control in some of the one- and two-dimensional traffic flow dynamical models in the mean field theory is studied.One dimensional model is investigated taking into account the effect of random delay. Two dimensional model takes into account the effects of overpasses, symmetric distribution of cars and blockages of cars moving in the same direction. Chaos synchronization is performed within both replica and nonreplica approaches, and using parameter perturbation method.
Self-control of traffic lights and vehicle flows in urban road networks
Lämmer, Stefan; Helbing, Dirk
2008-04-01
Based on fluid-dynamic and many-particle (car-following) simulations of traffic flows in (urban) networks, we study the problem of coordinating incompatible traffic flows at intersections. Inspired by the observation of self-organized oscillations of pedestrian flows at bottlenecks, we propose a self-organization approach to traffic light control. The problem can be treated as a multi-agent problem with interactions between vehicles and traffic lights. Specifically, our approach assumes a priority-based control of traffic lights by the vehicle flows themselves, taking into account short-sighted anticipation of vehicle flows and platoons. The considered local interactions lead to emergent coordination patterns such as 'green waves' and achieve an efficient, decentralized traffic light control. While the proposed self-control adapts flexibly to local flow conditions and often leads to non-cyclical switching patterns with changing service sequences of different traffic flows, an almost periodic service may evolve under certain conditions and suggests the existence of a spontaneous synchronization of traffic lights despite the varying delays due to variable vehicle queues and travel times. The self-organized traffic light control is based on an optimization and a stabilization rule, each of which performs poorly at high utilizations of the road network, while their proper combination reaches a superior performance. The result is a considerable reduction not only in the average travel times, but also of their variation. Similar control approaches could be applied to the coordination of logistic and production processes.
Integrated Traffic Flow Management Decision Making
Grabbe, Shon R.; Sridhar, Banavar; Mukherjee, Avijit
2009-01-01
A generalized approach is proposed to support integrated traffic flow management decision making studies at both the U.S. national and regional levels. It can consider tradeoffs between alternative optimization and heuristic based models, strategic versus tactical flight controls, and system versus fleet preferences. Preliminary testing was accomplished by implementing thirteen unique traffic flow management models, which included all of the key components of the system and conducting 85, six-hour fast-time simulation experiments. These experiments considered variations in the strategic planning look-ahead times, the replanning intervals, and the types of traffic flow management control strategies. Initial testing indicates that longer strategic planning look-ahead times and re-planning intervals result in steadily decreasing levels of sector congestion for a fixed delay level. This applies when accurate estimates of the air traffic demand, airport capacities and airspace capacities are available. In general, the distribution of the delays amongst the users was found to be most equitable when scheduling flights using a heuristic scheduling algorithm, such as ration-by-distance. On the other hand, equity was the worst when using scheduling algorithms that took into account the number of seats aboard each flight. Though the scheduling algorithms were effective at alleviating sector congestion, the tactical rerouting algorithm was the primary control for avoiding en route weather hazards. Finally, the modeled levels of sector congestion, the number of weather incursions, and the total system delays, were found to be in fair agreement with the values that were operationally observed on both good and bad weather days.
Noise-Induced Phase Transition in Traffic Flow
Institute of Scientific and Technical Information of China (English)
LI Ke-Ping; GAO Zi-You
2004-01-01
One of the dynamic phases of the traffic flow is the traffic jam. It appears in traffic flow when the vehicledensity is larger than the critical value. In this paper, a new method is presented to investigate the traffic jam when thevehicle density is smaller than the critical value. In our method, we introduce noise into the traffic system after sufficienttransient time. Under the effect of noise, the traffic jam appears, and the phase transition from tree to synchronized flowoccurs in traffic flow. Our method is tested for the deterministic NaSch traffic model. The simulation results demonstratethat there exist a broad range of lower densities at which the noise effect leading to traffic jam can be observed.
Real-Time Corrected Traffic Correlation Model for Traffic Flow Forecasting
Directory of Open Access Journals (Sweden)
Hua-pu Lu
2015-01-01
Full Text Available This paper focuses on the problems of short-term traffic flow forecasting. The main goal is to put forward traffic correlation model and real-time correction algorithm for traffic flow forecasting. Traffic correlation model is established based on the temporal-spatial-historical correlation characteristic of traffic big data. In order to simplify the traffic correlation model, this paper presents correction coefficients optimization algorithm. Considering multistate characteristic of traffic big data, a dynamic part is added to traffic correlation model. Real-time correction algorithm based on Fuzzy Neural Network is presented to overcome the nonlinear mapping problems. A case study based on a real-world road network in Beijing, China, is implemented to test the efficiency and applicability of the proposed modeling methods.
Intercities traffic flow: linear and nonlinear models
Otero, Dino; Mizrahi, Salomon S
2016-01-01
We simulate the traffic of vehicles circulating within a network formed by sites (cities, car-rental agencies, etc.) connected by two-way roads or highways, to which we shall refer generically as intercity traffic. Our aim is to forecast the flux of the vehicles for $n$ consecutive days, by taking as prior knowledge previous observations. The formal tools used in our analysis consists in: (1) making use of digraphs that allow the visualization and schematization of the problem, where edges correspond to roads, etc. and the vertices with loops represent the sites. (2) From an initial set of transition probabilities, that form a Markov chain, or from an empirical distribution of vehicles at the vertices and edges, we construct the Markov matrix which is a stochastic matrix (SM), and assume that the evolution of the traffic flows according to the power $n$ of the SM and, (3) the use of the Perron-Frobenius theory to analyze the outcomes. We identify several modes or regimes before the distribution of vehicles at...
Stability analysis of traffic flow with extended CACC control models
Ya-Zhou, Zheng; Rong-Jun, Cheng; Siu-Ming, Lo; Hong-Xia, Ge
2016-06-01
To further investigate car-following behaviors in the cooperative adaptive cruise control (CACC) strategy, a comprehensive control system which can handle three traffic conditions to guarantee driving efficiency and safety is designed by using three CACC models. In this control system, some vital comprehensive information, such as multiple preceding cars’ speed differences and headway, variable safety distance (VSD) and time-delay effect on the traffic current and the jamming transition have been investigated via analytical or numerical methods. Local and string stability criterion for the velocity control (VC) model and gap control (GC) model are derived via linear stability theory. Numerical simulations are conducted to study the performance of the simulated traffic flow. The simulation results show that the VC model and GC model can improve driving efficiency and suppress traffic congestion. Project supported by the National Natural Science Foundation of China (Grant Nos. 71571107 and 11302110). The Scientific Research Fund of Zhejiang Province, China (Grant Nos. LY15A020007, LY15E080013, and LY16G010003). The Natural Science Foundation of Ningbo City (Grant Nos. 2014A610030 and 2015A610299), the Fund from the Government of the Hong Kong Administrative Region, China (Grant No. CityU11209614), and the K C Wong Magna Fund in Ningbo University, China.
Disorder effect on the traffic flow behavior
Ez-Zahraouy, H.; Benyoussef, A.
2008-08-01
The effects of some disorders, on the traffic flow behavior, are studied numerically. Especially, the effect of mixture of vehicles of different velocities and/or lengths, the effects of different drivers reactions, the position and the extraction rate of off-ramp in the free way. Using a generalized optimal velocity model, for a mixture of fast and slow vehicles, we have investigated the effect of delay times τ f and τ s on the fundamental diagram. It is Found that the small delay times have almost no effect, while, for sufficiently large delay time τ s , the current profile displays qualitatively five different forms, depending on τ f , τ s and the fractions f f and f s of the fast and slow cars, respectively. The velocity (current) exhibits first-order transitions at low and/or high densities, from freely moving phase to the congested state, and from congested state to a jamming one, respectively. The minimal current appears in intermediate values of τ s . Furthermore there exist, a critical value of τ f above which the meta-stability and hysteresis appear. The effects of disorder due to drivers behaviors have been introduced through a random delay time τ allowing the car to reach its optimal velocity traffic flow models with open boundaries. In the absence of the variation of the delay time Δτ, it is found that the transition from unstable to meta-stable and from meta-stable to stable state occur under the effect of the injecting and the extracting rate probabilities α and β respectively. Moreover, the perturbation of the traffic flow behavior due to the off-ramp has been studied using numerical simulations in the one dimensional cellular automaton traffic flow model with open boundaries. When the off-ramp is located between two critical positions i c1 and i c2 the current remains constant (plateau) for β0 c1 < β0 < β0 c2, and the density undergoes two successive first order transitions: from high density to plateau current phase and from average
Traffic states and jamming transitions induced by a bus in two-lane traffic flow
Nagai, Ryoichi; Nagatani, Takashi; Taniguchi, Naoki
2005-05-01
We study the traffic states and jamming transitions induced by a bus (slow car) in a two-lane traffic of cars. We use the dynamic model which is an extended one of the optimal velocity model to take into account the lane changing. The fundamental (flow-density) diagram is presented. The fundamental diagram changes highly by introducing a bus on a two-lane roadway. It is found that there are the six distinct states for the two-lane traffic flow including a bus. The spatio-temporal patterns are presented for the distinct traffic states. The dynamical state of traffic changes with density of cars. It is shown that the dynamical transitions among the distinct traffic states occur at some values of density. The phase diagram (region map) is shown for the two-lane traffic flow including a bus.
Abnormal traffic flow data detection based on wavelet analysis
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Xiao Qian
2016-01-01
Full Text Available In view of the traffic flow data of non-stationary, the abnormal data detection is difficult.proposed basing on the wavelet analysis and least squares method of abnormal traffic flow data detection in this paper.First using wavelet analysis to make the traffic flow data of high frequency and low frequency component and separation, and then, combined with least square method to find abnormal points in the reconstructed signal data.Wavelet analysis and least square method, the simulation results show that using wavelet analysis of abnormal traffic flow data detection, effectively reduce the detection results of misjudgment rate and false negative rate.
From Cellular Attractor Selection to Adaptive Signal Control for Traffic Networks
Tian, Daxin; Zhou, Jianshan; Sheng, Zhengguo; Wang, Yunpeng; Ma, Jianming
2016-03-01
The management of varying traffic flows essentially depends on signal controls at intersections. However, design an optimal control that considers the dynamic nature of a traffic network and coordinates all intersections simultaneously in a centralized manner is computationally challenging. Inspired by the stable gene expressions of Escherichia coli in response to environmental changes, we explore the robustness and adaptability performance of signalized intersections by incorporating a biological mechanism in their control policies, specifically, the evolution of each intersection is induced by the dynamics governing an adaptive attractor selection in cells. We employ a mathematical model to capture such biological attractor selection and derive a generic, adaptive and distributed control algorithm which is capable of dynamically adapting signal operations for the entire dynamical traffic network. We show that the proposed scheme based on attractor selection can not only promote the balance of traffic loads on each link of the network but also allows the global network to accommodate dynamical traffic demands. Our work demonstrates the potential of bio-inspired intelligence emerging from cells and provides a deep understanding of adaptive attractor selection-based control formation that is useful to support the designs of adaptive optimization and control in other domains.
Kinetic derivation of a Hamilton-Jacobi traffic flow model
Borsche, Raul; Kimathi, Mark
2012-01-01
Kinetic models for vehicular traffic are reviewed and considered from the point of view of deriving macroscopic equations. A derivation of the associated macroscopic traffic flow equations leads to different types of equations: in certain situations modified Aw-Rascle equations are obtained. On the other hand, for several choices of kinetic parameters new Hamilton-Jacobi type traffic equations are found. Associated microscopic models are discussed and numerical experiments are presented discussing several situations for highway traffic and comparing the different models.
A new dynamic model for heterogeneous traffic flow
Tang, T. Q.; Huang, H. J.; Zhao, S. G.; Shang, H. Y.
2009-06-01
Based on the property of heterogeneous traffic flow, we in this Letter present a new car-following model. Applying the relationship between the micro and macro variables, a new dynamic model for heterogeneous traffic flow is obtained. The fundamental diagram and the jam density of the heterogeneous traffic flow consisting of bus and car are studied under three different conditions: (1) without any restrictions, (2) under the action of the traffic control policy that restrains some private cars and (3) using bus to replace the private cars restrained by the traffic control policy. The numerical results show that our model can describe some qualitative properties of the heterogeneous traffic flow consisting of bus and car, which verifies that our model is reasonable.
Capacity of Multi-vehicle-types Mixed Traffic Flow
Institute of Scientific and Technical Information of China (English)
LI Wen-quan; WANG Wei; DENG Wei
2001-01-01
Based on the gap acceptance theory, the mixed traffic flow composed of r representative typesflows on the unsignalized intersection is set up. It is an extension of capacity model for one type vehicletraffic flow, and it is very fitter to the Chinese highway traffic condition than the other models.
A Realistic Cellular Automaton Model for Synchronized Traffic Flow
Institute of Scientific and Technical Information of China (English)
ZHAO Bo-Han; HU Mao-Bin; JIANG Rui; WU Qing-Song
2009-01-01
A cellular automaton model is proposed to consider the anticipation effect in drivers' behavior. It is shown that the anticipation effect can be one of the origins of synchronized traffic flow. With anticipation effect, the congested traffic flow simulated by the model exhibits the features of synchronized flow. The spatiotemporal patterns induced by an on-ramp are also consistent with the three-phaee traffic theory. Since the origin of synchronized flow is still controversial, our work can shed some light on the mechanism of synchronized flow.
Effect of violating the traffic light rule in the Biham-Middleton-Levine traffic flow model
Ding, Zhong-Jun; Jiang, Rui; Li, Ming; Li, Qi-Lang; Wang, Bing-Hong
2012-09-01
This paper studies the effect of violating the traffic light rule in the Biham-Middleton-Levine (BML) traffic flow model. It is assumed that there are two kinds of drivers: normal drivers obey the traffic light rule and violators disobey it. Simulation results show that although the existence of violators increases the average velocity in the free-flowing phase, it decreases the threshold from free-flowing phase to jam. With the presence of violators, a new kind of configuration with stripe slopes -2 and -1/2 has been found in the free-flowing phase. We have developed an analytical investigation which successfully predicts the average velocity in the free-flowing phase. A phase separation phenomenon, where jams and freely flowing traffic coexist, has been found in the intermediate car density range. The mechanism of the phase separation has been illustrated.
Dynamic characteristics and simulation of traffic flow with slope
Institute of Scientific and Technical Information of China (English)
He Hong-Di; Lu Wei-Zhen; Xue Yu; Dong Li-Yun
2009-01-01
This paper proposes a new traffic model to describe traffic flow with slope under consideration of the gravity effect. Based on the model, stability analysis is conducted and a numerical simulation is performed to explore the characteristics of the traffic flow with slope. The result shows that the perturbation of the system is an inherent one,which is induced by the slope. In addition, the hysteresis loop is represented through plotting the figure of velocity against headway and highly depends on the slope angle. The kinematic wave at high density is also obtained through reproducing the phenomenon of stop-and-go traffic, which is significant to explore the phase transition of traffic flow and the evolution of traffic congestion.
Traffic Signals Control with Adaptive Fuzzy Controller in Urban Road Network
Institute of Scientific and Technical Information of China (English)
LI Yan; FAN Xiao-ping
2008-01-01
An adaptive fuzzy logic controller (AFC) is presented for the signal control of the urban traffic network.The AFC is composed of the signal control system-oriented control level and the signal controller-oriented fuzzy rules regulation level.The control level decides the signal tunings in an intersection with a fuzzy logic controller.The regulation level optimizes the fuzzy rules by the Adaptive Rule Module in AFC according to both the system performance index in current control period and the traffic flows in the last one.Consequently the system performances are improved.A weight coefficient controller (WCC) is also developed to describe the interactions of traffic flow among the adjacent intersections.So the AFC combined with the WCC can be applied in a road network for signal timings.Simulations of the AFC on a real traffic scenario have been conducted.Simulation results indicate that the adaptive controller for traffic control shows better performance than the actuated one.
Simple cellular automaton model for traffic breakdown, highway capacity, and synchronized flow.
Kerner, Boris S; Klenov, Sergey L; Schreckenberg, Michael
2011-10-01
We present a simple cellular automaton (CA) model for two-lane roads explaining the physics of traffic breakdown, highway capacity, and synchronized flow. The model consists of the rules "acceleration," "deceleration," "randomization," and "motion" of the Nagel-Schreckenberg CA model as well as "overacceleration through lane changing to the faster lane," "comparison of vehicle gap with the synchronization gap," and "speed adaptation within the synchronization gap" of Kerner's three-phase traffic theory. We show that these few rules of the CA model can appropriately simulate fundamental empirical features of traffic breakdown and highway capacity found in traffic data measured over years in different countries, like characteristics of synchronized flow, the existence of the spontaneous and induced breakdowns at the same bottleneck, and associated probabilistic features of traffic breakdown and highway capacity. Single-vehicle data derived in model simulations show that synchronized flow first occurs and then self-maintains due to a spatiotemporal competition between speed adaptation to a slower speed of the preceding vehicle and passing of this slower vehicle. We find that the application of simple dependences of randomization probability and synchronization gap on driving situation allows us to explain the physics of moving synchronized flow patterns and the pinch effect in synchronized flow as observed in real traffic data.
Stochastic evolutions of dynamic traffic flow modeling and applications
Chen, Xiqun (Michael); Shi, Qixin
2015-01-01
This book reveals the underlying mechanisms of complexity and stochastic evolutions of traffic flows. Using Eulerian and Lagrangian measurements, the authors propose lognormal headway/spacing/velocity distributions and subsequently develop a Markov car-following model to describe drivers’ random choices concerning headways/spacings, putting forward a stochastic fundamental diagram model for wide scattering flow-density points. In the context of highway onramp bottlenecks, the authors present a traffic flow breakdown probability model and spatial-temporal queuing model to improve the stability and reliability of road traffic flows. This book is intended for researchers and graduate students in the fields of transportation engineering and civil engineering.
Effects of Car Accidents on Three-Lane Traffic Flow
Directory of Open Access Journals (Sweden)
Jianzhong Chen
2014-01-01
Full Text Available A three-lane traffic flow model is proposed to investigate the effect of car accidents on the traffic flow. The model is an extension of the full velocity difference (FVD model by taking into account the lane changing. The extended lane-changing rules are presented to model the lane-changing behaviour. The cases that the car accidents occupy the exterior or interior lane, the medium lane, and two lanes are studied by numerical simulations. The time-space diagrams and the current diagrams are presented, and the traffic jams are investigated. The results show that the car accident has a different effect on the traffic flow when it occupies different lanes. The car accidents have a more serious effect on the whole road when they occupy two lanes. The larger the density is, the greater the influence on the traffic flow becomes.
Enhancement and stabilization of traffic flow by moving in groups.
Kurata, S; Nagatani, T
2001-07-01
We study the traffic behavior of vehicles moving in groups analytically and numerically. A car-following model of traffic is extended to take into account a binary mixture of vehicles. It is shown that the movement in groups stabilizes the traffic flow. The jamming transition among the free traffic, the inhomogeneous traffic, and the homogeneous congested traffic occurs at a higher density than the threshold of the original model. The traffic current is highly enhanced at a high-density region by keeping a short headway without jam. The jamming transition is analyzed by using the linear stability method. It is found that the theoretical neutral stability curve agrees with the transition line obtained by the simulation.
Chaotic jam and phase transition in traffic flow with passing.
Nagatani, T
1999-08-01
The lattice hydrodynamic model is presented to take into account the passing effect in one-dimensional traffic flow. When the passing constant gamma is small, the conventional jamming transition occurs between the uniform traffic and kink density wave flows. When passing constant gamma is larger than the critical value, the jamming transitions occur from the uniform traffic flow, through the chaotic density wave flow, to the kink density wave flow, with an increasing delay time. The chaotic region increases with passing constant gamma. The neutral stability line is derived from the linear stability analysis. The neutral stability line coincides with the transition line between the uniform traffic and density wave flows. The modified Korteweg-de Vries equation describing the kink jam is derived for small values of gamma by use of a nonlinear analysis.
Microscopic modeling of multi-lane highway traffic flow
Hodas, N O
2003-01-01
In heavy traffic with congested roadway the maximum traffic flow also depends on length of cars. This is deduced in a simple derivation suited for classroom demonstration as well as homework. The resulting equation demonstrates a new relation to an apparently unrelated area of physics, the maximum ship velocity (hull speed) and explains why traffic is sometimes faster on the slow lane on a congested multi-lane road.
Research on the Method of Traffic Organization and Optimization Based on Dynamic Traffic Flow Model
Directory of Open Access Journals (Sweden)
Shu-bin Li
2017-01-01
Full Text Available The modern transportation system is becoming sluggish by traffic jams, so much so that it can harm the economic and society in our country. One of the reasons is the surging vehicles day by day. Another reason is the shortage of the traffic supply seriously. But the most important reason is that the traffic organization and optimization hardly met the conditions of modern transport development. In this paper, the practical method of the traffic organization and optimization used in regional area is explored by the dynamic traffic network analysis method. Firstly, the operational states of the regional traffic network are obtained by simulation method based on the self-developed traffic simulation software DynaCHINA, in which the improved traffic flow simulation model was proposed in order to be more suitable for actual domestic urban transport situation. Then the appropriated optimization model and algorithm were proposed according to different optimized content and organization goals, and the traffic simulation processes more suitable to regional optimization were designed exactly. Finally, a regional network in Tai’an city was selected as an example. The simulation results show that the proposed method is effective and feasible. It can provide strong scientific and technological support for the traffic management department.
Tri-level programming model for combined urban traffic signal control and traffic flow guidance
Institute of Scientific and Technical Information of China (English)
孙智源; 陆化普; 屈闻聪
2016-01-01
In order to balance the temporal-spatial distribution of urban traffic flow, a model is established for combined urban traffic signal control and traffic flow guidance. With consideration of the wide use of fixed signal control at intersections, traffic assignment under traffic flow guidance, and dynamic characteristics of urban traffic management, a tri-level programming model is presented. To reflect the impact of intersection delay on traffic assignment, the lower level model is set as a modified user equilibrium model. The middle level model, which contains several definitional constraints for different phase modes, is built for the traffic signal control optimization. To solve the problem of tide lane management, the upper level model is built up based on nonlinear 0-1 integer programming. A heuristic iterative optimization algorithm (HIOA) is set up to solve the tri-level programming model. The lower level model is solved by method of successive averages (MSA), the middle level model is solved by non-dominated sorting genetic algorithm II (NSGA II), and the upper level model is solved by genetic algorithm (GA). A case study is raised to show the efficiency and applicability of the proposed modelling and computing method.
A cellular automaton model for ship traffic flow in waterways
Qi, Le; Zheng, Zhongyi; Gang, Longhui
2017-04-01
With the development of marine traffic, waterways become congested and more complicated traffic phenomena in ship traffic flow are observed. It is important and necessary to build a ship traffic flow model based on cellular automata (CAs) to study the phenomena and improve marine transportation efficiency and safety. Spatial discretization rules for waterways and update rules for ship movement are two important issues that are very different from vehicle traffic. To solve these issues, a CA model for ship traffic flow, called a spatial-logical mapping (SLM) model, is presented. In this model, the spatial discretization rules are improved by adding a mapping rule. And the dynamic ship domain model is considered in the update rules to describe ships' interaction more exactly. Take the ship traffic flow in the Singapore Strait for example, some simulations were carried out and compared. The simulations show that the SLM model could avoid ship pseudo lane-change efficiently, which is caused by traditional spatial discretization rules. The ship velocity change in the SLM model is consistent with the measured data. At finally, from the fundamental diagram, the relationship between traffic ability and the lengths of ships is explored. The number of ships in the waterway declines when the proportion of large ships increases.
The fundamental diagram : a macroscopic traffic flow model.
Botma, H.
1976-01-01
In models of traffic flow, the interactions between vehicles are of prime interest, and are based on characteristics of the drivers, road and vehicles. The fundamental diagram is a representation of a relationship on a macroscopic level in the steady state between the quantity of traffic and a chara
Mori, Kazuo; Naito, Katsuhiro; Kobayashi, Hideo
The traffic adaptive 2-level active period control has been proposed as a traffic adaptation mechanism to handle temporal and spatial (geographical) traffic fluctuations in cluster-based wireless sensor networks (WSNs) employing IEEE802.15.4 medium access control (MAC). This paper proposes a traffic adaptive distributed backoff control mechanism for cluster-based WSNs with the traffic adaptive 2-level active period control to enhance the system performance, especially transmission performance. The proposed mechanism autonomously adjusts the starting time of the backoff procedure for channel accesses in the contention access period (CAP) specified by the IEEE802.15.4 MAC, and then distributes the channel access timing over a wide range within the CAP, which can mitigate channel access congestion. The results of computer simulations show that the proposed mechanism can improve the transmission delay performance while keeping the enhancement in throughput and energy consumption at the cluster-based WSNs under non-uniform traffic environments.
Jam-avoiding adaptive cruise control (ACC) and its impact on traffic dynamics
Kesting, A; Kranke, F; Sch"onhof, M; Treiber, M; Helbing, Dirk; Kesting, Arne; Kranke, Florian; Sch\\"onhof, Martin; Treiber, Martin
2006-01-01
Adaptive-Cruise Control (ACC) automatically accelerates or decelerates a vehicle to maintain a selected time gap, to reach a desired velocity, or to prevent a rear-end collision. To this end, the ACC sensors detect and track the vehicle ahead for measuring the actual distance and speed difference. Together with the own velocity, these input variables are exactly the same as in car-following models. The focus of this contribution is: What will be the impact of a spreading of ACC systems on the traffic dynamics? Do automated driving strategies have the potential to improve the capacity and stability of traffic flow or will they necessarily increase the heterogeneity and instability? How does the result depend on the ACC equipment level? We discuss microscopic modeling aspects for human and automated (ACC) driving. By means of microscopic traffic simulations, we study how a variable percentage of ACC-equipped vehicles influences the stability of traffic flow, the maximum flow under free traffic conditions until ...
Social dilemma structure hidden behind traffic flow with route selection
Tanimoto, Jun; Nakamura, Kousuke
2016-10-01
Several traffic flows contain social dilemma structures. Herein, we explored a route-selection problem using a cellular automaton simulation dovetailed with evolutionary game theory. In our model, two classes of driver-agents coexist: D agents (defective strategy), which refer to traffic information for route selection to move fast, and C agents (cooperative strategy), which are insensitive to information and less inclined to move fast. Although no evidence suggests that the social dilemma structure in low density causes vehicles to move freely and that in high density causes traffic jams, we found a structure that corresponds to an n-person (multiplayer) Chicken (n-Chicken) game if the provided traffic information is inappropriate. If appropriate traffic information is given to the agents, the n-Chicken game can be solved. The information delivered to vehicles is crucial for easing the social dilemma due to urban traffic congestion when developing technologies to support the intelligent transportation system (ITS).
Controlling Disorder in Traffic Flow by Perturbation
Institute of Scientific and Technical Information of China (English)
LIKe-Ping; GAOZi-You; CHENTian-Lun
2004-01-01
We propose a new technique for controlling disorder in traffic system. A kind of control signal which can be considered as a perturbation has been designated at a given site (perturbation point) of the single-lane highway. When a vehicle passes the perturbation point at a time, the velocity of the vehicle will be changed at the next time by the perturbation. This technique is tested for the deterministic NaSch traffic model. The simulation results indicate that the traffic system can be transited from the disorder states to the order states, such as fixed-point, periodic motion, etc.
Agent-Based Collaborative Traffic Flow Management Project
National Aeronautics and Space Administration — We propose agent-based game-theoretic approaches for simulation of strategies involved in multi-objective collaborative traffic flow management (CTFM). Intelligent...
Accurate Multisteps Traffic Flow Prediction Based on SVM
Directory of Open Access Journals (Sweden)
Zhang Mingheng
2013-01-01
Full Text Available Accurate traffic flow prediction is prerequisite and important for realizing intelligent traffic control and guidance, and it is also the objective requirement for intelligent traffic management. Due to the strong nonlinear, stochastic, time-varying characteristics of urban transport system, artificial intelligence methods such as support vector machine (SVM are now receiving more and more attentions in this research field. Compared with the traditional single-step prediction method, the multisteps prediction has the ability that can predict the traffic state trends over a certain period in the future. From the perspective of dynamic decision, it is far important than the current traffic condition obtained. Thus, in this paper, an accurate multi-steps traffic flow prediction model based on SVM was proposed. In which, the input vectors were comprised of actual traffic volume and four different types of input vectors were compared to verify their prediction performance with each other. Finally, the model was verified with actual data in the empirical analysis phase and the test results showed that the proposed SVM model had a good ability for traffic flow prediction and the SVM-HPT model outperformed the other three models for prediction.
Realistic Data-Driven Traffic Flow Animation Using Texture Synthesis.
Chao, Qianwen; Deng, Zhigang; Ren, Jiaping; Ye, Qianqian; Jin, Xiaogang
2017-01-11
We present a novel data-driven approach to populate virtual road networks with realistic traffic flows. Specifically, given a limited set of vehicle trajectories as the input samples, our approach first synthesizes a large set of vehicle trajectories. By taking the spatio-temporal information of traffic flows as a 2D texture, the generation of new traffic flows can be formulated as a texture synthesis process, which is solved by minimizing a newly developed traffic texture energy. The synthesized output captures the spatio-temporal dynamics of the input traffic flows, and the vehicle interactions in it strictly follow traffic rules. After that, we position the synthesized vehicle trajectory data to virtual road networks using a cage-based registration scheme, where a few traffic-specific constraints are enforced to maintain each vehicle's original spatial location and synchronize its motion in concert with its neighboring vehicles. Our approach is intuitive to control and scalable to the complexity of virtual road networks. We validated our approach through many experiments and paired comparison user studies.
An improved BP artificial neural network algorithm for urban traffic flow intelligent prediction
Institute of Scientific and Technical Information of China (English)
XIONG Shi-yong; ZHANG Yi
2009-01-01
The traffic flow is interrelated to traffic congestion, the big traffic flow directly results in traffic congestion of some section. In this paper, on the basis of the research of overseas traffic accident, considering the characteristic of Chinese traffic, artificial neural network was used to predict traffic accident, and an improved BP artificial neural network model according with Chinese the situation of a country was proposed. The urban traffic flow prediction was simulated under the particular situation, the simulation result shows that the improved BP artificial neural network can fit the urban traffic flow prediction very well and have high performance.
Synchronized flow and wide moving jams from balanced vehicular traffic
Siebel, F; Siebel, Florian; Mauser, Wolfram
2005-01-01
Recently we proposed an extension to the traffic model of Aw, Rascle and Greenberg. The extended traffic model can be written as a hyperbolic system of balance laws and numerically reproduces the reverse $\\lambda$ shape of the fundamental diagram of traffic flow. In the current work we analyze the steady state solutions of the new model and their stability properties. In addition to the equilibrium flow curve the trivial steady state solutions form two additional branches in the flow-density diagram. We show that the characteristic structure excludes parts of these branches resulting in the reverse $\\lambda$ shape of the flow-density relation. The upper branch is metastable against the formation of synchronized flow for intermediate densities and unstable for high densities, whereas the lower branch is unstable for intermediate densities and metastable for high densities. Moreover, the model can reproduce the typical speed of the downstream front of wide moving jams. It further reproduces a constant outflow f...
Traffic Flow States in a Freeway with Bottleneck
Institute of Scientific and Technical Information of China (English)
PENG Zi-Hui; SUN Gang; ZHU Jing-Yi
2009-01-01
The system of mixture of single lane and double lane is studied by a cellular automata model, which is developed by us based on the Nagel and Schreckenberg's models. We justify that the model can reach a stable states quickly. The density distributions of the stable state is presented for several cases, which illustrate the manner of the congestion. The relationship between the outflow rate and the total number of vehicles and that between the outflow rate and the density just before the bottleneck are both given. Comparing with the relationship that occurring in the granular flow, we conclude that the transition from the free traffic flow to the congested traffic flow can also be attributed to the abrupt variation through unstable flow state, which can naturally explain the discontinuities and the complex time variation behavior observed in the traffic flow experiments.
Kerner, B. S.; Klenov, S. L.; Brakemeier, A.
2009-01-01
Effects of vehicle-to-vehicle (or/and vehicle-to-infrastructure communication, called also V2X communication)on traffic flow, which are relevant for ITS, are numerically studied. To make the study adequate with real measured traffic data, a testbed for wireless vehicle communication based on a microscopic model in the framework of three-phase traffic theory is developed and discussed. In this testbed, vehicle motion in traffic flow and analyses of a vehicle communication channel access based ...
KINEMATIC WAVE PROPERTIES OF ANISOTROPIC DYNAMICS MODEL FOR TRAFFIC FLOW
Institute of Scientific and Technical Information of China (English)
姜锐; 吴清松; 朱祚金
2002-01-01
The analyses of kinematic wave properties of a new dynamics model for traffic flow are carried out. The model does not exhibit the problem that one characteristic speed is always greater than macroscopic traffic speed, and therefore satisfies the requirement that traffic flow is anisotropic. Linear stability analysis shows that the model is stable under certain condition and the condition is obtained. The analyses also indicate that the model has a hierarchy of first-and second-order waves, and allows the existence of both smooth traveling wave and shock wave. However, the model has a distinctive criterion of shock wave compared with other dynamics models, and the distinction makes the model more realistic in dealing with some traffic problems such as wrong-way travel analysis.
AN OVERVIEW OF LONGITUDINAL CHARACTERISTICS OF ROAD TRAFFIC FLOW
Directory of Open Access Journals (Sweden)
Banihan GÜNAY
2002-02-01
Full Text Available As multi-lane roadways have been widely used in many countries for years, analysis of two-dimensional vehicular interactions acquires special importance in highway design and operation. The simultaneous consideration of both lateral and longitudinal movements of traffic flow becomes vital in many aspects of traffic engineering, like modelling. The former component was reviewed elsewhere. In this paper, previous work on longitudinal characteristics of multi-lane traffic flow is scrutinised. Non-existence of such a review in recent literature was the main motive of the work, and it is hoped that it forms a reference report for other traffic analysts. In addition, the paper underlines a number of possible areas for future research.
Macroscopic modeling for traffic flow on three-lane highways
Chen, Jianzhong; Fang, Yuan
2015-04-01
In this paper, a macroscopic traffic flow model for three-lane highways is proposed. The model is an extension of the speed gradient model by taking into account the lane changing. The new source and sink terms of lane change rate are added into the continuity equations and the speed dynamic equations to describe the lane-changing behavior. The result of the steady state analysis shows that our model can describe the lane usage inversion phenomenon. The numerical results demonstrate that the present model effectively reproduces several traffic phenomena observed in real traffic such as shock and rarefaction waves, stop-and-go waves and local clusters.
Influence of Darkness on Motorway Traffic Flow Characteristics
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Johnnie Ben-Edigbe
2014-06-01
Full Text Available The study is aimed at estimating the influence of darkness on motorways during dry weather. In a ‘with-and-without’ impact studies, motorway traffic flow characteristics at two different locations in Malaysia were investigated. Travel speed, traffic flow and headway data were obtained continuously for six weeks at selected sites and supplemented with darkness and daylight data culled from Malaysian Metrological Department website. Start of pitch darkness time was given as 19.45 pm. The study used 22:00 pm as start of pitch darkness. Results show that maximum flow rate, optimum travel speed, critical density and optimum headway did not differ significantly. The study concluded that motorway traffic flow characteristics are not influenced by darkness significantly.
Effect of multi-velocity-difference in traffic flow
Institute of Scientific and Technical Information of China (English)
Mo Ye-Liu; He Hong-Di; Xue Yu; Shi Wei; Lu Wei-Zhen
2008-01-01
Based on the optimal velocity models, an extended model is proposed, in which multi-velocity-difference ahead is taken into consideration. The damping effect of the multi-velocity-difference ahead has been investigated by means of analytical and numerical methods. Results indicate that the multi-velocity-difference leads to the enhancement of stability of traffic flow, suppression of the emergence of traffic jamming, and reduction of the energy consumption.
Short-term traffic flow forecasting with A-SVARMA
2013-01-01
PUBLISHED Short-term Traffic Flow Forecasting (STFF), the process of predicting future traffic conditions based on historical and real-time observations, is an essential aspect of Intelligent Transportation Systems (ITS). The existing well-known algorithms used for STFF include time-series analysis based techniques, among which the seasonal Autoregressive Moving Average (ARMA) model is one of the most precise methods used in this field. The effectiveness of STFF in an urban transport netwo...
Routing strategies in traffic network and phase transition in network traffic flow
Indian Academy of Sciences (India)
Bing-Hong Wang; Wen-Xu Wang
2008-08-01
The dynamics of information traffic over scale-free networks has been investigated systematically. A series of routing strategies of data packets have been proposed, including the local routing strategy, the next-nearest-neighbour routing strategy, and the mixed routing strategy based on local static and dynamic information. The capacity of the network can be quantified by the phase transition from free flow state to congestion state. The optimal parameter values of each model leading to the highest efficiency of scale-free networked traffic systems have been found. Moreover, we have found hysteretic loop in networked traffic systems with finite packets delivering ability. Such hysteretic loop indicates the existence of the bi-stable state in the traffic dynamics over scale-free networks.
Impacts of Snowy Weather Conditions on Expressway Traffic Flow Characteristics
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Jiancheng Weng
2013-01-01
Full Text Available Snowy weather will significantly degrade expressway operations, reduce service levels, and increase driving difficulty. Furthermore, the impact of snow varies in different types of roads, diverse cities, and snow densities due to different driving behavior. Traffic flow parameters are essential to decide what should be appropriate for weather-related traffic management and control strategies. This paper takes Beijing as a case study and analyzes traffic flow data collected by detectors in expressways. By comparing the performance of traffic flow under normal and snowy weather conditions, this paper quantitatively describes the impact of adverse weather on expressway volume and average speeds. Results indicate that average speeds on the Beijing expressway under heavy snow conditions decrease by 10–20 km/h when compared to those under normal weather conditions, the vehicle headway generally increases by 2–4 seconds, and the road capacity drops by about 33%. This paper also develops a specific expressway traffic parameter reduction model which proposes reduction coefficients of expressway volumes and speeds under various snow density conditions in Beijing. The conclusions paper provide effective foundational parameters for urban expressway controls and traffic management under snow conditions.
Digital Advertising Traffic Operation: Flow Management Analysis
Mas, Massimiliano Dal
2017-01-01
In a Web Advertising Traffic Operation the Trafficking Routing Problem (TRP) consists in scheduling the management of Web Advertising (Adv) campaign between Trafficking campaigns in the most efficient way to oversee and manage relationship with partners and internal teams, managing expectations through integration and post-launch in order to ensure success for every stakeholders involved. For our own interest we did that independent research projects also through specific innovative tasks val...
The effect of ACC vehicles to mixed traffic flow consisting of manual and ACC vehicles
Institute of Scientific and Technical Information of China (English)
Xie Dong-Fan; Gao Zi-You; Zhao Xiao-Mei
2008-01-01
This paper studies the effect of adaptive cruise control (ACC) system on traffic flow by using simulations. The multiple headway and velocity difference (MHVD) model is used to depict the motion of ACC vehicles, and the simulation results are compared with the optimal velocity (OV) model which is used to depict the motion of manual vehicles.Compared the cases between the manual and the ACC vehicle flow, the fundamental diagram can be classified into four regions: I, II, III, IV. In low and high density the flux of the two models is the same; in region Ⅱ the free flow region of the MHVD model is enlarged, and the flux of the MHVD model is larger than that of the OV model; in region Ⅲ serious jams occur in the OV model while the ACC system suppresses the jams in the MHVD model and the traffic flow is in order, but the flux of the OV model is larger than that of the MHVD model. Similar phenomena also appeared in mixed traffic flow which consists of manual and ACC vehicles. The results indicate that ACC vehicles have significant effect on traffic flow. The improvement induced by ACC vehicles decreases with the increasing proportion of ACC vehicles.
Impact of distracted driving on safety and traffic flow.
Stavrinos, Despina; Jones, Jennifer L; Garner, Annie A; Griffin, Russell; Franklin, Crystal A; Ball, David; Welburn, Sharon C; Ball, Karlene K; Sisiopiku, Virginia P; Fine, Philip R
2013-12-01
Studies have documented a link between distracted driving and diminished safety; however, an association between distracted driving and traffic congestion has not been investigated in depth. The present study examined the behavior of teens and young adults operating a driving simulator while engaged in various distractions (i.e., cell phone, texting, and undistracted) and driving conditions (i.e., free flow, stable flow, and oversaturation). Seventy five participants 16-25 years of age (split into 2 groups: novice drivers and young adults) drove a STISIM simulator three times, each time with one of three randomly presented distractions. Each drive was designed to represent daytime scenery on a 4 lane divided roadway and included three equal roadway portions representing Levels of Service (LOS) A, C, and E as defined in the 2000 Highway Capacity Manual. Participants also completed questionnaires documenting demographics and driving history. Both safety and traffic flow related driving outcomes were considered. A Repeated Measures Multivariate Analysis of Variance was employed to analyze continuous outcome variables and a Generalized Estimate Equation (GEE) Poisson model was used to analyze count variables. Results revealed that, in general more lane deviations and crashes occurred during texting. Distraction (in most cases, text messaging) had a significantly negative impact on traffic flow, such that participants exhibited greater fluctuation in speed, changed lanes significantly fewer times, and took longer to complete the scenario. In turn, more simulated vehicles passed the participant drivers while they were texting or talking on a cell phone than while undistracted. The results indicate that distracted driving, particularly texting, may lead to reduced safety and traffic flow, thus having a negative impact on traffic operations. No significant differences were detected between age groups, suggesting that all drivers, regardless of age, may drive in a manner
Calvert, S.C.; Snelder, M.
2016-01-01
Traffic is affected by a wide range of variables. An influential and commonly occurring variable on traffic flow is the weather. Weather conditions affect both traffic demand as well as road capacity and in doing so also affect the traffic fluency, or rather the ability of traffic to maintain a cert
Dynamic evaluation of traffic flows on city roads
Institute of Scientific and Technical Information of China (English)
Quan Yongshen; Guo Jifu; Wen Huimin; Sun Jianping
2012-01-01
This paper presents an analysis of the random fluctuations, deferred conduction effect and periodicity of road traffic based on the basic features of road networks. It also discusses the limitations of road network evaluation theories based on road ＂V/C＂. In addition, it proposes a set of theoretical and technical methods for the real-time evaluation of traffic flows for entire road networks, and for solving key technical issues, such as real-time data collection and process- ing in areas with no blind zones, the spatial-temporal dynamic analysis of road network traffic, and the calibration of key performance index thresholds. It also provides new technical tools for the strategic transportation planning and real-time diagnosis of road traffic. The new tools and methodology presented in this paper are validated using a case study in Beijing.
OPTIMIZATION OF URBAN MULTI-INTERSECTION TRAFFIC FLOW VIA Q-LEARNING
Directory of Open Access Journals (Sweden)
Yit Kwong Chin
2013-01-01
Full Text Available Congestions of the traffic flow within the urban traffic network have been a challenging task for all the urban developers. Many approaches have been introduced into the current system to solve the traffic congestion problems. Reconfiguration of the traffic signal timing plan has been carried out through implementation of different techniques. However, dynamic characteristics of the traffic flow increase the difficulties towards the ultimate solutions. Thus, traffic congestions still remain as unsolvable problems to the current traffic control system. In this study, artificial intelligence method has been introduced in the traffic light system to alter the traffic signal timing plan to optimize the traffic flows. Q-learning algorithm in this study has enhanced the traffic light system with learning ability. The learning mechanism of Q-learning enables traffic light intersections to release itself from traffic congestions situation. Adjacent traffic light intersections will work independently and yet cooperate with each others to a common goal of ensuring the fluency of the traffic flows within the traffic network. The simulated results show that the Q-Learning algorithm is able to learn from the dynamic traffic flow and optimize the traffic flow accordingly.
Evolutionary Concepts for Decentralized Air Traffic Flow Management
Adams, Milton; Kolitz, Stephan; Milner, Joseph; Odoni, Amedeo
1997-01-01
Alternative concepts for modifying the policies and procedures under which the air traffic flow management system operates are described, and an approach to the evaluation of those concepts is discussed. Here, air traffic flow management includes all activities related to the management of the flow of aircraft and related system resources from 'block to block.' The alternative concepts represent stages in the evolution from the current system, in which air traffic management decision making is largely centralized within the FAA, to a more decentralized approach wherein the airlines and other airspace users collaborate in air traffic management decision making with the FAA. The emphasis in the discussion is on a viable medium-term partially decentralized scenario representing a phase of this evolution that is consistent with the decision-making approaches embodied in proposed Free Flight concepts for air traffic management. System-level metrics for analyzing and evaluating the various alternatives are defined, and a simulation testbed developed to generate values for those metrics is described. The fundamental issue of modeling airline behavior in decentralized environments is also raised, and an example of such a model, which deals with the preservation of flight bank integrity in hub airports, is presented.
Phase transitions in traffic flow on multilane roads.
Kerner, Boris S; Klenov, Sergey L
2009-11-01
Based on empirical and numerical analyses of vehicular traffic, the physics of spatiotemporal phase transitions in traffic flow on multilane roads is revealed. The complex dynamics of moving jams observed in single vehicle data measured by video cameras on American highways is explained by the nucleation-interruption effect in synchronized flow, i.e., the spontaneous nucleation of a narrow moving jam with the subsequent jam dissolution. We find that (i) lane changing, vehicle merging from on-ramps, and vehicle leaving to off-ramps result in different traffic phases-free flow, synchronized flow, and wide moving jams-occurring and coexisting in different road lanes as well as in diverse phase transitions between the traffic phases; (ii) in synchronized flow, the phase transitions are responsible for a non-regular moving jam dynamics that explains measured single vehicle data: moving jams emerge and dissolve randomly at various road locations in different lanes; (iii) the phase transitions result also in diverse expanded general congested patterns occurring at closely located bottlenecks.
Phase transitions in traffic flow on multilane roads
Kerner, Boris S.; Klenov, Sergey L.
2009-11-01
Based on empirical and numerical analyses of vehicular traffic, the physics of spatiotemporal phase transitions in traffic flow on multilane roads is revealed. The complex dynamics of moving jams observed in single vehicle data measured by video cameras on American highways is explained by the nucleation-interruption effect in synchronized flow, i.e., the spontaneous nucleation of a narrow moving jam with the subsequent jam dissolution. We find that (i) lane changing, vehicle merging from on-ramps, and vehicle leaving to off-ramps result in different traffic phases—free flow, synchronized flow, and wide moving jams—occurring and coexisting in different road lanes as well as in diverse phase transitions between the traffic phases; (ii) in synchronized flow, the phase transitions are responsible for a non-regular moving jam dynamics that explains measured single vehicle data: moving jams emerge and dissolve randomly at various road locations in different lanes; (iii) the phase transitions result also in diverse expanded general congested patterns occurring at closely located bottlenecks.
Genomics of local adaptation with gene flow.
Tigano, Anna; Friesen, Vicki L
2016-05-01
Gene flow is a fundamental evolutionary force in adaptation that is especially important to understand as humans are rapidly changing both the natural environment and natural levels of gene flow. Theory proposes a multifaceted role for gene flow in adaptation, but it focuses mainly on the disruptive effect that gene flow has on adaptation when selection is not strong enough to prevent the loss of locally adapted alleles. The role of gene flow in adaptation is now better understood due to the recent development of both genomic models of adaptive evolution and genomic techniques, which both point to the importance of genetic architecture in the origin and maintenance of adaptation with gene flow. In this review, we discuss three main topics on the genomics of adaptation with gene flow. First, we investigate selection on migration and gene flow. Second, we discuss the three potential sources of adaptive variation in relation to the role of gene flow in the origin of adaptation. Third, we explain how local adaptation is maintained despite gene flow: we provide a synthesis of recent genomic models of adaptation, discuss the genomic mechanisms and review empirical studies on the genomics of adaptation with gene flow. Despite predictions on the disruptive effect of gene flow in adaptation, an increasing number of studies show that gene flow can promote adaptation, that local adaptations can be maintained despite high gene flow, and that genetic architecture plays a fundamental role in the origin and maintenance of local adaptation with gene flow.
Kerner, Boris S.
2014-03-01
Three-phase traffic flow theory of city traffic has been developed. Based on simulations of a stochastic microscopic traffic flow model, features of moving synchronized flow patterns (MSP) have been studied, which are responsible for a random time-delayed breakdown of a green-wave (GW) organized in a city. A possibility of GW control leading to the prevention of GW breakdown has been demonstrated. A diagram of traffic breakdown in under-saturated traffic (transition from under- to over-saturated city traffic) at the signal has been found; the diagram presents regions of the average arrival flow rate, within which traffic breakdown can occur, in dependence of parameters of the time-function of the arrival flow rate or/and signal parameters. Physical reasons for a crucial difference between results of classical theory of city traffic and three-phase theory are explained. In particular, we have found that under-saturated traffic at the signal can exist during a long time interval, when the average arrival flow rate is larger than the capacity of the classical theory; the classical capacity is equal to a minimum capacity in three-phase theory. Within a range of the average arrival flow rate between the minimum and maximum signal capacities, under-saturated traffic is in a metastable state with respect to traffic breakdown. We have distinguished the following possible causes for the metastability of under-saturated traffic: (i) The arrival flow rate during the green phase is larger than the saturation flow rate. (ii) The length of the upstream front of a queue at the signal is a finite value. (iii) The outflow rate from a MSP (the rate of MSP discharge) is larger than the saturation flow rate.
The influence of bus stop on traffic flow with velocity-difference-separation model
Zheng, Pengjun; Wang, Wei; Ge, Hongxia
2016-06-01
Based on velocity-difference-separation model, the mixed traffic flow on two-lane road is investigated. For a fixed road length, the influence of bus and bus stops on traffic flow is studied with the increasing traffic density. Compared with the result without bus stops given by Li et al., a new traffic state is found, which is valuable for studying the impacts of public transport on urban traffic flow.
Identifying online traffic based on property of TCP flow
Institute of Scientific and Technical Information of China (English)
HONG Min-huo; GU Ren-tao; WANG Hong-xiang; SUN Yong-mei; JI Yue-feng
2009-01-01
Classification of network traffic using port-based or payload-based analysis is becoming increasingly difficult when many applications use dynamic port numbers, masquerading techniques, and encryption to avoid detection. In this article, an approach is presented for online traffic classification relying on the observation of the first n packets of a transmission control protocol (TCP) connection. Its key idea is to utilize the properties of the observed first ten packets of a TCP connection and Bayesian network method to build a classifier. This classifier can classify TCP flows dynamically as packets pass through it by deciding whether a TCP flow belongs to a given application. The experimental results show that the proposed approach performs well in online Internet traffic classification and that it is superior to naive Bayesian method.
Analysis of the stability and density waves for traffic flow
Institute of Scientific and Technical Information of China (English)
薛郁
2002-01-01
In this paper, the optimal velocity model of traffic is extended to take into account the relative velocity. Thestability and density waves for traffic flow are investigated analytically with the perturbation method. The stabilitycriterion is derived by the linear stability analysis. It is shown that the triangular shock wave, soliton wave and kinkwave appear respectively in our model for density waves in the three regions: stable, metastable and unstable regions.These correspond to the solutions of the Burgers equation, Kortewegg-de Vries equation and modified Korteweg-de Vriesequation.The analytical results are confirmed to be in good agreement with those of numerical simulation. All theresults indicate that the interaction of a car with relative velocity can affect the stability of the traffic flow and raisecritical density.
Dynamic stochastic optimization models for air traffic flow management
Mukherjee, Avijit
This dissertation presents dynamic stochastic optimization models for Air Traffic Flow Management (ATFM) that enables decisions to adapt to new information on evolving capacities of National Airspace System (NAS) resources. Uncertainty is represented by a set of capacity scenarios, each depicting a particular time-varying capacity profile of NAS resources. We use the concept of a scenario tree in which multiple scenarios are possible initially. Scenarios are eliminated as possibilities in a succession of branching points, until the specific scenario that will be realized on a particular day is known. Thus the scenario tree branching provides updated information on evolving scenarios, and allows ATFM decisions to be re-addressed and revised. First, we propose a dynamic stochastic model for a single airport ground holding problem (SAGHP) that can be used for planning Ground Delay Programs (GDPs) when there is uncertainty about future airport arrival capacities. Ground delays of non-departed flights can be revised based on updated information from scenario tree branching. The problem is formulated so that a wide range of objective functions, including non-linear delay cost functions and functions that reflect equity concerns can be optimized. Furthermore, the model improves on existing practice by ensuring efficient use of available capacity without necessarily exempting long-haul flights. Following this, we present a methodology and optimization models that can be used for decentralized decision making by individual airlines in the GDP planning process, using the solutions from the stochastic dynamic SAGHP. Airlines are allowed to perform cancellations, and re-allocate slots to remaining flights by substitutions. We also present an optimization model that can be used by the FAA, after the airlines perform cancellation and substitutions, to re-utilize vacant arrival slots that are created due to cancellations. Finally, we present three stochastic integer programming
An Analysis of Vehicular Traffic Flow Using Langevin Equation
Directory of Open Access Journals (Sweden)
Çağlar Koşun
2015-08-01
Full Text Available Traffic flow data are stochastic in nature, and an abundance of literature exists thereof. One way to express stochastic data is the Langevin equation. Langevin equation consists of two parts. The first part is known as the deterministic drift term, the other as the stochastic diffusion term. Langevin equation does not only help derive the deterministic and random terms of the selected portion of the city of Istanbul traffic empirically, but also sheds light on the underlying dynamics of the flow. Drift diagrams have shown that slow lane tends to get congested faster when vehicle speeds attain a value of 25 km/h, and it is 20 km/h for the fast lane. Three or four distinct regimes may be discriminated again from the drift diagrams; congested, intermediate, and free-flow regimes. At places, even the intermediate regime may be divided in two, often with readiness to congestion. This has revealed the fact that for the selected portion of the highway, there are two main states of flow, namely, congestion and free-flow, with an intermediate state where the noise-driven traffic flow forces the flow into either of the distinct regimes.
Effect of desired speed variability on highway traffic flow.
Lipshtat, Azi
2009-06-01
Traffic flow is a function of many natural, environmental, and human factors. Not only that weather and road condition can vary, but drivers' decisions and policies also can affect the flow. Here we analyze the effect of distribution of desired speeds. We show that a broader distribution can reduce the flow efficiency and increase congestions. Since different drivers react differently to changes in weather or road conditions, such a change leads to a change in desired speed distribution as well. As a result, nonintuitive changes in traffic flow may occur. Besides providing insight and analyzing the underlying mechanism of a collective phenomenon, this example sheds light on a fundamental aspect of computational modeling. Although "mean-field" models that deal with average values only and ignore variability are simpler and easier to analyze, they can very easily turn into oversimplifications and miss relevant qualitative phenomena.
Traffic Management as a Service: The Traffic Flow Pattern Classification Problem
Directory of Open Access Journals (Sweden)
Carlos T. Calafate
2015-01-01
Full Text Available Intelligent Transportation System (ITS technologies can be implemented to reduce both fuel consumption and the associated emission of greenhouse gases. However, such systems require intelligent and effective route planning solutions to reduce travel time and promote stable traveling speeds. To achieve such goal these systems should account for both estimated and real-time traffic congestion states, but obtaining reliable traffic congestion estimations for all the streets/avenues in a city for the different times of the day, for every day in a year, is a complex task. Modeling such a tremendous amount of data can be time-consuming and, additionally, centralized computation of optimal routes based on such time-dependencies has very high data processing requirements. In this paper we approach this problem through a heuristic to considerably reduce the modeling effort while maintaining the benefits of time-dependent traffic congestion modeling. In particular, we propose grouping streets by taking into account real traces describing the daily traffic pattern. The effectiveness of this heuristic is assessed for the city of Valencia, Spain, and the results obtained show that it is possible to reduce the required number of daily traffic flow patterns by a factor of 4210 while maintaining the essence of time-dependent modeling requirements.
Halim, Herni; Abdullah, Ramdzani
2014-01-01
HIGHLIGHTS Highway traffic noise is a serious problem in Malaysia Heavy traffic flow highway recorded higher noise level compared to low traffic flow Noise level stabilized at certain number of vehicles on the road i.e above 500 vehicles. Although much research on road traffic noise has found that noise level increase are influenced by driver behavior and source-receiver distance, little attention has been paid to the relationship between noise level and total number of vehicles...
A Modified Cellular Automaton Model for Traffic Flow
Institute of Scientific and Technical Information of China (English)
葛红霞; 董力耘; 雷丽; 戴世强
2004-01-01
A modified cellular automaton model for traffic flow was proposed. A novel concept about the changeable security gap was introduced and a parameter related to the variable security gap was determined. The fundamental diagram obtained by simulation shows that the maximum flow more approaches to the observed data than that of the NaSch model, indicating that the presented model is more reasonable and realistic.
Li, Zhipeng; Zhong, Chenjie; Chen, Lizhu; Xu, Shangzhi; Qian, Yeqing
2016-09-01
In this paper, the original lattice hydrodynamic model of traffic flow is extended to take into account the traffic current cooperation among three consecutive sites. The basic idea of the new consideration is that the cooperative traffic current of the considered site is determined by the traffic currents of the site itself, the immediately preceding site and the immediately following one. The stability criterion of the extended model is obtained by applying the linear stability analysis. The result reveals the traffic current cooperation of the immediately preceding site is positive correlation with the stability of traffic system, while negative correlation is found between the traffic stability and the traffic current cooperation of the nearest follow site. To describe the phase transition, the modified KdV equation near the critical point is derived by using the reductive perturbation method, with obtaining the dependence of the propagation kink solution for traffic jams on the traffic current cooperation among three consecutive sites. The direct numerical are conducted to verify the results of theoretical analysis, and explore the effects of the traffic current cooperation on the traffic flux of the vehicle flow system.
The Effect of the Relative Velocity on Traffic Flow
Institute of Scientific and Technical Information of China (English)
XUE Yu; DONG Li-Yun; YUAN Yi-Wu; DAI Shi-Qiang
2002-01-01
The optimal velocity model of traffc is extended to take the relative velocity into account. The traffcbehavior is investigated numerically and analytically with this model. It is shown that the car interaction with therelative velocity can effect the stability of the traffic flow and raise critical density. The jamming transition between thefreely moving and jamming phases is investigated with the linear stability analysis and nonlinear perturbation methods.The traffic jam is described by the kink solution of the modified Korteweg-de Vries equation. The theoretical result isin good agreement with the simulation.
Continuum modeling for two-lane traffic flow
Institute of Scientific and Technical Information of China (English)
Haijun Huang; Tieqiao Tang; Ziyou Gao
2006-01-01
In this paper,we study the continuum modeling of traffic dynamics for two-lane freeways.A new dynamics model is proposed, which contains the speed gradient-based momentum equations derived from a car-following theory suited to two-lane traffic flow.The conditions for securing the linear stability of the new model are presented.Numerical tests are carried out and some nonequilibrium phenomena are observed, such as small disturbance instability,stop-andgo waves,local clusters and phase transition.
Characteristic particle methods for traffic flow simulations on highway networks
Farjoun, Yossi
2012-01-01
A characteristic particle method for the simulation of first order macroscopic traffic models on road networks is presented. The approach is based on the method "particleclaw", which solves scalar one dimensional hyperbolic conservations laws exactly, except for a small error right around shocks. The method is generalized to nonlinear network flows, where particle approximations on the edges are suitably coupled together at the network nodes. It is demonstrated in numerical examples that the resulting particle method can approximate traffic jams accurately, while only devoting a few degrees of freedom to each edge of the network.
Tian, Junfang; Li, Geng; Treiber, Martin; Zhu, Chenqiang; Jia, Bin
2016-01-01
This paper firstly show that 2 Dimensional Intelligent Driver Model (Jiang et al., PloS one, 9(4), e94351, 2014) is not able to replicate the synchronized traffic flow. Then we propose an improved model by considering the difference between the driving behaviors at high speeds and that at low speeds. Simulations show that the improved model can reproduce the phase transition from synchronized flow to wide moving jams, the spatiotemporal patterns of traffic flow induced by traffic bottleneck, and the evolution concavity of traffic oscillations (i.e. the standard deviation of the velocities of vehicles increases in a concave/linear way along the platoon). Validating results show that the empirical time series of traffic speed obtained from Floating Car Data can be well simulated as well.
Directory of Open Access Journals (Sweden)
Georges Arnaout
2011-12-01
Full Text Available Purpose: In this paper, the impact of Cooperative Adaptive Cruise Control (CACC systems on traffic performance is examined using microscopic agent-based simulation. Using a developed traffic simulation model of a freeway with an on-ramp - created to induce perturbations and to trigger stop-and-go traffic, the CACC system’s effect on the traffic performance is studied. The previously proposed traffic simulation model is extended and validated. By embedding CACC vehicles in different penetration levels, the results show significance and indicate the potential of CACC systems to improve traffic characteristics and therefore can be used to reduce traffic congestion. The study shows that the impact of CACC is positive but is highly dependent on the CACC market penetration. The flow rate of the traffic using CACC is proportional to the market penetration rate of CACC equipped vehicles and the density of the traffic.Design/methodology/approach: This paper uses microscopic simulation experiments followed by a quantitative statistical analysis. Simulation enables researchers manipulating the system variables to straightforwardly predict the outcome on the overall system, giving researchers the unique opportunity to interfere and make improvements to performance. Thus with simulation, changes to variables that might require excessive time, or be unfeasible to carry on real systems, are often completed within seconds.Findings: The findings of this paper are summarized as follow:•\tProvide and validate a platform (agent-based microscopic traffic simulator in which any CACC algorithm (current or future may be evaluated.•\tProvide detailed analysis associated with implementation of CACC vehicles on freeways.•\tInvestigate whether embedding CACC vehicles on freeways has a significant positive impact or not.Research limitations/implications: The main limitation of this research is that it has been conducted solely in a computer laboratory. Laboratory
Design of Optical Wireless Networks with Fair Traffic Flows
Directory of Open Access Journals (Sweden)
Artur Tomaszewski
2014-01-01
Full Text Available The paper presents a method for optimising the wireless optical network that carries elastic packet traffic. The particular focus is on modelling the effect of elastic traffic flows slowing down in response to the decrease of the optical transmission systems’ capacity at bad weather conditions. A mathematical programming model of the network design problem is presented that assumes that the packet rates of elastic traffic flows decrease fairly. While practically any subset of network links can be simultaneously affected by unfavourable transmission conditions, a particular challenge of solving the problem results from a huge number of network states considered in the model. Therefore, how the problem can be solved by generating the most unfavourable network states is presented. Moreover, it is proved that it is entirely sufficient to consider only the states that correspond to the decrease of capacity on a single link. Finally, as the general problem is nonlinear, it is shown that the problem can be transformed to a linear MIP problem and solved effectively when single-path routing of traffic flows is assumed.
Towards a macroscopic modeling of the complexity in traffic flow.
Rosswog, Stephan; Wagner, Peter
2002-03-01
Based on the assumption of a safe velocity U(e)(rho) depending on the vehicle density rho, a macroscopic model for traffic flow is presented that extends the model of the Kühne-Kerner-Konhäuser by an interaction term containing the second derivative of U(e)(rho). We explore two qualitatively different forms of U(e): a conventional Fermi-type function and, motivated by recent experimental findings, a function that exhibits a plateau at intermediate densities, i.e., in this density regime the exact distance to the car ahead is only of minor importance. To solve the fluid-like equations a Lagrangian particle scheme is developed. The suggested model shows a much richer dynamical behavior than the usual fluid-like models. A large variety of encountered effects is known from traffic observations, many of which are usually assigned to the elusive state of "synchronized flow." Furthermore, the model displays alternating regimes of stability and instability at intermediate densities. It can explain data scatter in the fundamental diagram and complicated jam patterns. Within this model, a consistent interpretation of the emergence of very different traffic phenomena is offered: they are determined by the velocity relaxation time, i.e., the time needed to relax towards U(e)(rho). This relaxation time is a measure of the average acceleration capability and can be attributed to the composition (e.g., the percentage of trucks) of the traffic flow.
Chao, Kuei-Hsiang; Chen, Pi-Yun
2014-01-01
This study primarily focuses on the use of radio frequency identification (RFID) as a form of traffic flow detection, which transmits collected information related to traffic flow directly to a control system through an RS232 interface. At the same time, the sensor analyzes and judges the information using an extension algorithm designed to achieve the objective of controlling the flow of traffic. In addition, the traffic flow situation is also transmitted to a remote monitoring control syste...
Adaptive EWMA Method Based on Abnormal Network Traffic for LDoS Attacks
Directory of Open Access Journals (Sweden)
Dan Tang
2014-01-01
Full Text Available The low-rate denial of service (LDoS attacks reduce network services capabilities by periodically sending high intensity pulse data flows. For their concealed performance, it is more difficult for traditional DoS detection methods to detect LDoS attacks; at the same time the accuracy of the current detection methods for LDoS attacks is relatively low. As the fact that LDoS attacks led to abnormal distribution of the ACK traffic, LDoS attacks can be detected by analyzing the distribution characteristics of ACK traffic. Then traditional EWMA algorithm which can smooth the accidental error while being the same as the exceptional mutation may cause some misjudgment; therefore a new LDoS detection method based on adaptive EWMA (AEWMA algorithm is proposed. The AEWMA algorithm which uses an adaptive weighting function instead of the constant weighting of EWMA algorithm can smooth the accidental error and retain the exceptional mutation. So AEWMA method is more beneficial than EWMA method for analyzing and measuring the abnormal distribution of ACK traffic. The NS2 simulations show that AEWMA method can detect LDoS attacks effectively and has a low false negative rate and a false positive rate. Based on DARPA99 datasets, experiment results show that AEWMA method is more efficient than EWMA method.
Soliton and kink jams in traffic flow with open boundaries.
Muramatsu, M; Nagatani, T
1999-07-01
Soliton density wave is investigated numerically and analytically in the optimal velocity model (a car-following model) of a one-dimensional traffic flow with open boundaries. Soliton density wave is distinguished from the kink density wave. It is shown that the soliton density wave appears only at the threshold of occurrence of traffic jams. The Korteweg-de Vries (KdV) equation is derived from the optimal velocity model by the use of the nonlinear analysis. It is found that the traffic soliton appears only near the neutral stability line. The soliton solution is analytically obtained from the perturbed KdV equation. It is shown that the soliton solution obtained from the nonlinear analysis is consistent with that of the numerical simulation.
Speed limit and ramp meter control for traffic flow networks
Goatin, Paola; Göttlich, Simone; Kolb, Oliver
2016-07-01
The control of traffic flow can be related to different applications. In this work, a method to manage variable speed limits combined with coordinated ramp metering within the framework of the Lighthill-Whitham-Richards (LWR) network model is introduced. Following a 'first-discretize-then-optimize' approach, the first order optimality system is derived and the switch of speeds at certain fixed points in time is explained, together with the boundary control for the ramp metering. Sequential quadratic programming methods are used to solve the control problem numerically. For application purposes, experimental setups are presented wherein variable speed limits are used as a traffic guidance system to avoid traffic jams on highway interchanges and on-ramps.
Network Traffic Anomalies Detection and Identification with Flow Monitoring
Nguyen, Huy; Kim, Dong Il; Choi, Deokjai
2010-01-01
Network management and security is currently one of the most vibrant research areas, among which, research on detecting and identifying anomalies has attracted a lot of interest. Researchers are still struggling to find an effective and lightweight method for anomaly detection purpose. In this paper, we propose a simple, robust method that detects network anomalous traffic data based on flow monitoring. Our method works based on monitoring the four predefined metrics that capture the flow statistics of the network. In order to prove the power of the new method, we did build an application that detects network anomalies using our method. And the result of the experiments proves that by using the four simple metrics from the flow data, we do not only effectively detect but can also identify the network traffic anomalies.
An evolutionary outlook of air traffic flow management techniques
Kistan, Trevor; Gardi, Alessandro; Sabatini, Roberto; Ramasamy, Subramanian; Batuwangala, Eranga
2017-01-01
In recent years Air Traffic Flow Management (ATFM) has become pertinent even in regions without sustained overload conditions caused by dense traffic operations. Increasing traffic volumes in the face of constrained resources has created peak congestion at specific locations and times in many areas of the world. Increased environmental awareness and economic drivers have combined to create a resurgent interest in ATFM as evidenced by a spate of recent ATFM conferences and workshops mediated by official bodies such as ICAO, IATA, CANSO the FAA and Eurocontrol. Significant ATFM acquisitions in the last 5 years include South Africa, Australia and India. Singapore, Thailand and Korea are all expected to procure ATFM systems within a year while China is expected to develop a bespoke system. Asia-Pacific nations are particularly pro-active given the traffic growth projections for the region (by 2050 half of all air traffic will be to, from or within the Asia-Pacific region). National authorities now have access to recently published international standards to guide the development of national and regional operational concepts for ATFM, geared to Communications, Navigation, Surveillance/Air Traffic Management and Avionics (CNS+A) evolutions. This paper critically reviews the field to determine which ATFM research and development efforts hold the best promise for practical technological implementations, offering clear benefits both in terms of enhanced safety and efficiency in times of growing air traffic. An evolutionary approach is adopted starting from an ontology of current ATFM techniques and proceeding to identify the technological and regulatory evolutions required in the future CNS+A context, as the aviation industry moves forward with a clearer understanding of emerging operational needs, the geo-political realities of regional collaboration and the impending needs of global harmonisation.
AN INTELLIGENT TRAFFIC LIGHTS CONTROL ALGORITHM BASED ON TRAFFIC FLOW%基于车流量的交通灯智能控制算法
Institute of Scientific and Technical Information of China (English)
王鼎湘; 李茂军
2015-01-01
随着道路交通流量日益增加，现有交通灯使用的时间固定控制方法并不能很好地满足各种复杂交通情况。针对这一背景，在使用视频图像对车辆跟踪计数实时采集车流量的基础上，提出一种根据各方向车流量控制交通灯时间的算法。该算法根据实时的车流情况更新各方向的绿灯分配时间，自动调节各方向绿灯时间比例，并根据路口总车流量的大小智能调节绿灯时间周期大小。基于 Delphi 平台对算法进行仿真，结果表明：该算法能根据实时车流信息自适应调整各方向绿灯时长，并通过自动调节各方向绿灯时间总和来有效实现交通拥堵或畅通情况下交通灯的智能控制。%The time-fixed control method used by existing traffic lights can not well satisfy various complicated traffic conditions along with the increasingly growth of road traffic flow.Under this background and based on the acquisition of real-time traffic flow by using video images to track and count vehicles,we propose an algorithm of controlling traffic lights time according to the traffic flow from various directions.This algorithm updates the allocated time for green lights in each direction based upon real-time traffic situation and automatically adjusts the time scale of green lights in various directions.It also intelligently regulates the size of the time cycle of green lights according to the total traffic flow on intersections.The algorithm is simulated based on Delphi platform,the results show that the proposed algorithm can adaptively adjust the time length of green lights in each direction based on real-time vehicles traffic information,and effectively realises the intelligent traffic lights control in the circumstances of traffic congestion or in smooth flow by automatically adjusting the total time of green lights in different di-rections.
Concept definition of traffic flow wide-area surveillance
Energy Technology Data Exchange (ETDEWEB)
Allgood, G.O.; Ferrell, R.K.; Kercel, S.W.
1994-07-01
Traffic management can be thought of as a stochastic queuing process where the serving time at one of its control points is dynamically linked to the global traffic pattern, which is, in turn, dynamically linked to the control point. For this closed-loop system to be effective, the traffic management system must sense and interpret large spatial projections of data originating from multiple sensor suites. The intent of the Wide-Area Surveillance (WAS) Project is to build upon this concept and define the operational specifications and characteristics of a Traffic Flow Wide-Area Surveillance (TFWAS) system in terms of traffic management and control. In doing so, the functional capabilities of a TFWAS will be mapped onto an operational profile that is consistent with the Federal Highway Administration`s Intelligent Vehicle Highway System. This document provides the underlying foundation of this work by offering a concept definition for the TFWAS system. It concentrates on answering the question: ``What is the system?`` In doing so, the report develops a hierarchy of specialized definitions.
Directory of Open Access Journals (Sweden)
Hemant Kumar Sharma
2012-06-01
Full Text Available Speed–flow functions have been developed by several transportation experts to predict accurately the speed of urban road network. HCM Speed-Flow Curve, BPR Curve, MTC Speed-Flow Curve, Akçelik Speed-Flow Curve are some extraordinary efforts to define the shape of speed-flow curve. However, the complexity of driver’s behaviour, interactions among different type of vehicles, lateral clearance, co-relation of driver’s psychology with vehicular characteristics and interdependence of various variables of traffic has led to continuous development and refinement of speed-flow curves. The problem gets more tedious in case of urban roads with heterogeneous traffic, oversaturated flow and signalized network (which includes some unsignalized intersections as well. This paper presents speed-flow analysis for urban roads with interrupted flow comprising of heterogeneous traffic. Model has been developed for heterogeneous traffic under constraints of roadway geometry, vehicle characteristics, driving behaviour and traffic controls. The model developed in this paper shall predict speed, delay, average queue and maximum queue estimates for urban roads and quantify congestion for oversaturated condition. The investigation details oversaturated portion of flow in particular.
A refined and dynamic cellular automaton model for pedestrian-vehicle mixed traffic flow
Liu, Mianfang; Xiong, Shengwu
2016-12-01
Mixed traffic flow sharing the “same lane” and having no discipline on road is a common phenomenon in the developing countries. For example, motorized vehicles (m-vehicles) and nonmotorized vehicles (nm-vehicles) may share the m-vehicle lane or nm-vehicle lane and pedestrians may share the nm-vehicle lane. Simulating pedestrian-vehicle mixed traffic flow consisting of three kinds of traffic objects: m-vehicles, nm-vehicles and pedestrians, can be a challenge because there are some erratic drivers or pedestrians who fail to follow the lane disciplines. In the paper, we investigate various moving and interactive behavior associated with mixed traffic flow, such as lateral drift including illegal lane-changing and transverse crossing different lanes, overtaking and forward movement, and propose some new moving and interactive rules for pedestrian-vehicle mixed traffic flow based on a refined and dynamic cellular automaton (CA) model. Simulation results indicate that the proposed model can be used to investigate the traffic flow characteristic in a mixed traffic flow system and corresponding complicated traffic problems, such as, the moving characteristics of different traffic objects, interaction phenomenon between different traffic objects, traffic jam, traffic conflict, etc., which are consistent with the actual mixed traffic system. Therefore, the proposed model provides a solid foundation for the management, planning and evacuation of the mixed traffic flow.
Microcanonical and canonical approach to traffic flow
Surda, Anton
2007-01-01
A system of identical cars on a single-lane road is treated as a microcanonical and canonical ensemble. Behaviour of the cars is characterized by the probability of car velocity as a function of distance and velocity of the car ahead. The calculations a performed on a discrete 1D lattice with discrete car velocities. Probability of total velocity of a group of cars as a function of density is calculated in microcanonical approach. For a canonical ensemble, fluctuations of car density as a function of total velocity is found. Phase transitions between free and jammed flow for large deceleration rate of cars and formation of queues of cars with the same velocity for low deceleration rate are described.
CONTROLLING TRAFFIC FLOW IN MULTILANE-ISOLATED INTERSECTION USING ANFIS APPROACH TECHNIQUES
2015-01-01
Many controllers have applied the Adaptive Neural-Fuzzy Inference System (ANFIS) concept for optimizing the controller performance. However, there are less traffic signal controllers developed using the ANFIS concept. ANFIS traffic signal controller with its fuzzy rule base and its ability to learn from a set of sample data could improve the performance of Existing traffic signal controlling system to reduce traffic congestions at most of the busy traffic intersections in city such as Kuala L...
S-MATE: Secure Coding-based Multipath Adaptive Traffic Engineering
Aly, Salah A; Walid, Anwar I; Poor, H Vincent
2010-01-01
There have been several approaches to provisioning traffic between core network nodes in Internet Service Provider (ISP) networks. Such approaches aim to minimize network delay, increase network capacity, and enhance network security services. MATE (Multipath Adaptive Traffic Engineering) protocol has been proposed for multipath adaptive traffic engineering between an ingress node (source) and an egress node (destination). Its novel idea is to avoid network congestion and attacks that might exist in edge and node disjoint paths between two core network nodes. This paper builds an adaptive, robust, and reliable traffic engineering scheme for better performance of communication network operations. This will also provision quality of service (QoS) and protection of traffic engineering to maximize network efficiency. Specifically, we present a new approach, S-MATE (secure MATE) is developed to protect the network traffic between two core nodes (routers or switches) in a cloud network. S-MATE secures against a sin...
Traffic behavior of mixed traffic flow with two kinds of different self-stabilizing control vehicles
Li, Zhipeng; Li, Wenzhong; Xu, Shangzhi; Qian, Yeqing; Sun, Jian
2015-10-01
In this paper, we propose a heterogeneous car following model in terms of an extension to the original optimal velocity model characterizing two classes of different self-stabilizing control vehicles. Linear stability analysis method is utilized to the extended model, for purpose to explore how the varying percentages of the vehicles with short-duration self-stabilizing control influence the stability of the heterogeneous traffic flow. We obtain the neutral stability lines for different percentages of two classes of vehicles, with finding that the traffic flow trends to stable with the decrease of the percentage for short-duration self-stabilizing control vehicles. Moreover, we explore a special case that the same numbers of two different classes of vehicles with self-stabilizing control. We theoretically derive the stability condition of the special case, and conclude the effect of the average value and the standard deviation of two time gaps, on the heterogeneous traffic stability. At last, direct simulations are conducted to verify the conclusion of theoretical analysis.
Li, Run-Kui; Zhao, Tong; Li, Zhi-Peng; Ding, Wen-Jun; Cui, Xiao-Yong; Xu, Qun; Song, Xian-Feng
2014-04-01
On-road vehicle emissions have become the main source of urban air pollution and attracted broad attentions. Vehicle emission factor is a basic parameter to reflect the status of vehicle emissions, but the measured emission factor is difficult to obtain, and the simulated emission factor is not localized in China. Based on the synchronized increments of traffic flow and concentration of air pollutants in the morning rush hour period, while meteorological condition and background air pollution concentration retain relatively stable, the relationship between the increase of traffic and the increase of air pollution concentration close to a road is established. Infinite line source Gaussian dispersion model was transformed for the inversion of average vehicle emission factors. A case study was conducted on a main road in Beijing. Traffic flow, meteorological data and carbon monoxide (CO) concentration were collected to estimate average vehicle emission factors of CO. The results were compared with simulated emission factors of COPERT4 model. Results showed that the average emission factors estimated by the proposed approach and COPERT4 in August were 2.0 g x km(-1) and 1.2 g x km(-1), respectively, and in December were 5.5 g x km(-1) and 5.2 g x km(-1), respectively. The emission factors from the proposed approach and COPERT4 showed close values and similar seasonal trends. The proposed method for average emission factor estimation eliminates the disturbance of background concentrations and potentially provides real-time access to vehicle fleet emission factors.
Parameter estimation for stochastic hybrid model applied to urban traffic flow estimation
2015-01-01
This study proposes a novel data-based approach for estimating the parameters of a stochastic hybrid model describing the traffic flow in an urban traffic network with signalized intersections. The model represents the evolution of the traffic flow rate, measuring the number of vehicles passing a given location per time unit. This traffic flow rate is described using a mode-dependent first-order autoregressive (AR) stochastic process. The parameters of the AR process take different values dep...
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, J A; Molera, J M; Cuesta, José A; Martinez, Froilán C; Molera, Juan M
1993-01-01
Abstract: We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Phase Transitions in Two-Dimensional Traffic Flow Models
Cuesta, José A; Molera, Juan M; Escuela, Angel Sánchez; 10.1103/PhysRevE.48.R4175
2009-01-01
We introduce two simple two-dimensional lattice models to study traffic flow in cities. We have found that a few basic elements give rise to the characteristic phase diagram of a first-order phase transition from a freely moving phase to a jammed state, with a critical point. The jammed phase presents new transitions corresponding to structural transformations of the jam. We discuss their relevance in the infinite size limit.
Fuzzy Prediction for Traffic Flow Based on Delta Test
2016-01-01
This paper presents a novel approach to one-step-forward prediction of traffic flow based on fuzzy reasoning. The successful construction of a competent fuzzy inference system of Sugeno type largely relies on proper choice of input dimension and accurate estimation of structure parameters and rules. The first issue is addressed with a proposed method, based on δ-test, which can simultaneously determine input dimension and reduce noise level. In response to the second issue, two clustering tec...
Density waves in traffic flow of two kinds of vehicles.
Liu, Z Z; Zhou, X J; Liu, X M; Luo, J
2003-01-01
Through the car-following model, the traffic flow of two types of vehicles (cars and trucks) on a single-lane flow is studied, in which drivers on different vehicles have different sensitivities and the safety distance is assumed to be the same for all vehicles. The linear analysis is carried out to determine the condition of critical stability. With the nonlinear analysis, it proves that the small fluctuation of the vehicle density near the critical stable state satisfies the Korteweg-deVries equation and different sensitivities affect only the soliton evolution. When the headway in the critical state is more than the safety distance, the density around the soliton peak exceeds the density of the critical stable state, which can be explained as the formation of traffic jam. Contrarily, when the headway state is less than the safety distance, drivers will increase the headway to avoid the jam. The direct approach of the soliton perturbation shows that drivers' sensitivity will increase the soliton's amplitude continuously. Moreover, the increase of the number of trucks in the traffic flow will slow down the evolution of the amplitude.
Method for Traffic Flow Estimation using On-dashboard Camera Image
Directory of Open Access Journals (Sweden)
Kohei Arai
2014-02-01
Full Text Available This paper presents the method to estimate the traffic flow on the urban roadway by using car’s on-dashboard camera image. The system described, shows something new which utilizes only road traffic photo images to get the information about urban roadway traffic flow automatically.
Order-parameter model for unstable multilane traffic flow
Lubashevsky; Mahnke
2000-11-01
We discuss a phenomenological approach to the description of unstable vehicle motion on multilane highways that explains in a simple way the observed sequence of the "free flow synchronized mode jam" phase transitions as well as the hysteresis in these transitions. We introduce a variable called an order parameter that accounts for possible correlations in the vehicle motion at different lanes. So, it is principally due to the "many-body" effects in the car interaction in contrast to such variables as the mean car density and velocity being actually the zeroth and first moments of the "one-particle" distribution function. Therefore, we regard the order parameter as an additional independent state variable of traffic flow. We assume that these correlations are due to a small group of "fast" drivers and by taking into account the general properties of the driver behavior we formulate a governing equation for the order parameter. In this context we analyze the instability of homogeneous traffic flow that manifested itself in the above-mentioned phase transitions and gave rise to the hysteresis in both of them. Besides, the jam is characterized by the vehicle flows at different lanes which are independent of one another. We specify a certain simplified model in order to study the general features of the car cluster self-formation under the "free flow synchronized motion" phase transition. In particular, we show that the main local parameters of the developed cluster are determined by the state characteristics of vehicle motion only.
A probabilistic hypothesis density filter for traffic flow estimation in the presence of clutter
Canaud, Matthieu; MIHAYLOVA, Lyudmila; EL FAOUZI, Nour-Eddin; BILLOT, Romain; Sau, Jacques
2012-01-01
Prediction of traffic flow variables such as traffic volume, travel speed or travel time for a short time horizon is of paramount importance in traffic control. Hence, the data assimilation process in traffic modeling for estimation and prediction plays a key role. However, the increasing complexity, non-linearity and presence of various uncertainties (both in the measured data and models) are important factors affecting the traffic state prediction. To overcome this problem, new methodologie...
Robust PCA-Based Abnormal Traffic Flow Pattern Isolation and Loop Detector Fault Detection
Institute of Scientific and Technical Information of China (English)
JIN Xuexiang; ZHANG Yi; LI Li; HU Jianming
2008-01-01
One key function of intelligent transportation systems is to automatically detect abnormal traffic phenomena and to help further investigations of the cause of the abnormality. This paper describes a robust principal components analysis (RPCA)-based abnormal traffic flow pattern isolation and loop detector fault detection method. The results show that RPCA is a useful tool to distinguish regular traffic flow from abnor-mal traffic flow patterns caused by accidents and loop detector faults. This approach gives an effective traffic flow data pre-processing method to reduce the human effort in finding potential loop detector faults. The method can also be used to further investigate the causes of the abnormality.
Phase transition in evolution of traffic flow with scale-free property
Institute of Scientific and Technical Information of China (English)
Shen Bo; Gao Zi-You
2008-01-01
This paper investigates the behaviour of traffic flow in traffic systems with a new model based on the NaSch model and cluster approximation of mean-field theory.The proposed model aims at constructing a mapping relationship between the microcosmic behaviour and the macroscopic property of traffic flow.Results demonstrate that scale-free phenomenon of the evolution network becomes obvious when the density value of traffic flow reaches at the critical point of phase transition from free flow to traffic congestion,and jamming is limited in this scale-fres structure.
Yu, Shaowei; Zhao, Xiangmo; Xu, Zhigang; Zhang, Licheng
2016-11-01
To evaluate the effects of velocity difference changes with memory in the intelligent transportation environment on the dynamics and fuel consumptions of traffic flow, we first investigate the linkage between velocity difference changes with memory and car-following behaviors with the measured data in cities, and then propose an improved cooperative car-following model considering multiple velocity difference changes with memory in the cooperative adaptive cruise control strategy, finally carry out several numerical simulations under the periodic boundary condition and at signalized intersections to explore how velocity difference changes with memory affect car's velocity, velocity fluctuation, acceleration and fuel consumptions in the intelligent transportation environment. The results show that velocity difference changes with memory have obvious effects on car-following behaviors, that the improved cooperative car-following model can describe the phase transition of traffic flow and estimate the evolution of traffic congestion, that the stability and fuel economy of traffic flow simulated by the improved car-following model with velocity difference changes with memory is obviously superior to those without velocity difference changes, and that taking velocity difference changes with memory into account in designing the advanced adaptive cruise control strategy can significantly improve the stability and fuel economy of traffic flow.
Application of Chaos Theory in the Prediction of Motorised Traffic Flows on Urban Networks
Directory of Open Access Journals (Sweden)
Aderemi Adewumi
2016-01-01
Full Text Available In recent times, urban road networks are faced with severe congestion problems as a result of the accelerating demand for mobility. One of the ways to mitigate the congestion problems on urban traffic road network is by predicting the traffic flow pattern. Accurate prediction of the dynamics of a highly complex system such as traffic flow requires a robust methodology. An approach for predicting Motorised Traffic Flow on Urban Road Networks based on Chaos Theory is presented in this paper. Nonlinear time series modeling techniques were used for the analysis of the traffic flow prediction with emphasis on the technique of computation of the Largest Lyapunov Exponent to aid in the prediction of traffic flow. The study concludes that algorithms based on the computation of the Lyapunov time seem promising as regards facilitating the control of congestion because of the technique’s effectiveness in predicting the dynamics of complex systems especially traffic flow.
Varotto, S.F.; Hoogendoorn, R.G.; Van Arem, B.; Hoogendoorn, S.P.
2014-01-01
Automated driving potentially has a significant impact on traffic flow efficiency. Automated vehicles, which possess cooperative capabilities, are expected to reduce congestion levels for instance by increasing road capacity, by anticipating traffic conditions further downstream and also by accelera
A Queuing Model-Based System for Triggering Traffic Flow Management Algorithms Project
National Aeronautics and Space Administration — Next generation air traffic management systems are expected use multiple software tools and quantitative methods for managing traffic flow in the National Airspace....
Phase diagrams properties of the mixed traffic flow on a crossroad
Li, Qi-Lang; Wang, Bing-Hong; Liu, Mu-Ren
2010-11-01
Based on the Ishibashi and Fukui crossroad traffic flow model [Y. Ishibashi and M. Fukui. J. Phys. Soc. Japan. 70 (2001) 2793], mixed traffic flow (i.e., the fast and slow vehicles with different maximum velocities are mixed) is investigated in this work. According to the numerical simulation results and the principle for constructing the phase diagram, phase diagrams for mixed traffic flow are constructed. It is noted that the topology of these phase diagrams is similar to that of phase diagrams for homogeneous vehicles (which refers to slow vehicles only). From the phase diagrams, it is evident that mixed traffic flow is influenced by the mixing rate f (fraction of slow and fast vehicles) in regions II and V, but not in other regions. Although a mixture of fast and slow vehicles is introduced in the crossroad traffic flow model, the separation between phases in the phase diagrams remains linear. For a given q (the vehicle density on the northbound road), one flow plateau appears in regions IIx or IVy, while two maximum flow plateaus appear in region V in each of the phase diagrams. The maximum flow values in region V reflect the maximum traffic capacity for the traffic system as defined in this work. Since mixed traffic flow is a common phenomenon in real traffic, this work may offer help in real traffic simulations and traffic management.
Noise induced pattern formation of oscillation growth in traffic flow
Tian, Junfang; Treiber, Martin
2016-01-01
Noise is able to induce diverse patterns in physical and interdisciplinary extended systems. This Letter investigates the role of noise in pattern formation of traffic flow, which is a typical self-driven system far from equilibrium. We demonstrate that noise is necessary to correctly describe the observed spatiotemporal dynamics of growing traffic oscillation in the car following process. A heuristic analysis qualitatively explains the concave growth of the oscillation amplitude along the vehicles of a platoon. Based on this analysis, we propose a simple car-following model containing indifference regions and acceleration noise described by Brownian motion which reproduces well the experimental and empirical observations. Our study indicates that noise might also play an important role in pattern formation in other biological or socio-economic systems that are subject to stochasticity.
Effects of Right-Turn Vehicles on Traffic Flow
Shang, Hua-Yan; Huang, Hai-Jun; Wu, Wen-Xiang
In real traffic, the right-turn vehicles at intersections are not controlled by signal lights and their effects are neglected. In this paper, we develop a cellular automaton model to formulate the complicated turning behaviors of vehicles at intersections. Simulation results are quite in accord with the observation on the Beijing's 4th ring road. It is found that the right-turn vehicles may produce queue near the intersection, a short lane designed for right-turn has prominent effect in improving traffic flow, but, a too long lane for right-turn cannot further decrease the stop ratio as expected. These findings deepen our understanding on the effects of right-turn vehicles and may help the design and management of intersections.
A modified weighted probabilistic cellular automaton traffic flow model
Institute of Scientific and Technical Information of China (English)
Zhuang Qian; Jia Bin; Li Xin-Gang
2009-01-01
This paper modifies the weighted probabilistic cellular automaton model (Li X L,Kuang H,Song T,et al 2008Chin.Phys.B 17 2366) which considered a diversity of traffic behaviors under real traffic situations induced by various driving characters and habits.In the new model,the effects of the velocity at the last time step and drivers' desire for acceleration are taken into account.The fundamental diagram,spatial-temporal diagram,and the time series of one-minute data axe analyzed.The results show that this model reproduces synchronized flow.Finally,it simulates the on-ramp system with the proposed model.Some characteristics including the phase diagram are studied.
PRINCIPLES OF SAFETY MANAGEMENT OF AIR TRAFFIC FLOWS AND CAPACITY UNDER UNCERTAINTY CONDITIONS
Directory of Open Access Journals (Sweden)
Wang Bo
2016-11-01
Full Text Available Purpose: The aim of this study is to investigate the general principles of safety and capacity management in Aeronautical systems regarding air traffic flows operations under uncertainty conditions. In this work the theoretical framework assessing at the same time both the uncertainty model and flight plans model are proposed. Methods: To study features of safety of air traffic flows and capacity under uncertainty conditions were built the original probabilistic models including Bayesian Network for flight plan and air traffic control sector model based on Poisson Binomial Distribution. Results: We obtained models for safety management of air traffic flows and capacity under uncertainty conditions. We discussed appropriate approach for estimating the parameters of safety of air traffic flows and capacity under uncertainty and Markovian uncertainty model for the flight plan. Discussion: We developed the Bayesian Network for flight plan and air traffic control sector models for safety management of air traffic flows and capacity under uncertainty conditions.
Macroscopic Model and Simulation Analysis of Air Traffic Flow in Airport Terminal Area
Directory of Open Access Journals (Sweden)
Honghai Zhang
2014-01-01
Full Text Available We focus on the spatiotemporal characteristics and their evolvement law of the air traffic flow in airport terminal area to provide scientific basis for optimizing flight control processes and alleviating severe air traffic conditions. Methods in this work combine mathematical derivation and simulation analysis. Based on cell transmission model the macroscopic models of arrival and departure air traffic flow in terminal area are established. Meanwhile, the interrelationship and influential factors of the three characteristic parameters as traffic flux, density, and velocity are presented. Then according to such models, the macro emergence of traffic flow evolution is emulated with the NetLogo simulation platform, and the correlativity of basic traffic flow parameters is deduced and verified by means of sensitivity analysis. The results suggest that there are remarkable relations among the three characteristic parameters of the air traffic flow in terminal area. Moreover, such relationships evolve distinctly with the flight procedures, control separations, and ATC strategies.
Modeling, Identification, Estimation, and Simulation of Urban Traffic Flow in Jakarta and Bandung
Directory of Open Access Journals (Sweden)
Herman Y. Sutarto
2015-06-01
Full Text Available This paper presents an overview of urban traffic flow from the perspective of system theory and stochastic control. The topics of modeling, identification, estimation and simulation techniques are evaluated and validated using actual traffic flow data from the city of Jakarta and Bandung, Indonesia, and synthetic data generated from traffic micro-simulator VISSIM. The results on particle filter (PF based state estimation and Expectation-Maximization (EM based parameter estimation (identification confirm the proposed model gives satisfactory results that capture the variation of urban traffic flow. The combination of the technique and the simulator platform assembles possibility to develop a real-time traffic light controller.
Salden, Ron; Paas, Fred; Van Merriënboer, Jeroen
2008-01-01
Salden, R.J.C.M., Paas, F., & Van Merriënboer, J.J.G. (2006). Personalised adaptive task selection in air traffic control: Effects on training efficiency and transfer. Learning and Instruction, 16, 350-362
Monitoring individual traffic flows within the ATLAS TDAQ network
Energy Technology Data Exchange (ETDEWEB)
Sjoen, R; Batraneanu, S M; Leahu, L; Martin, B; Al-Shabibi, A [CERN, 1211 Geneva 23 (Switzerland); Stancu, S; Ciobotaru, M, E-mail: rune.velle.sjoen@cern.c [' Politehnica' University of Bucharest (Romania)
2010-04-01
The ATLAS data acquisition system consists of four different networks interconnecting up to 2000 processors using up to 200 edge switches and five multi-blade chassis devices. The architecture of the system has been described in [1] and its operational model in [2]. Classical, SNMP-based, network monitoring provides statistics on aggregate traffic, but for performance monitoring and troubleshooting purposes there was an imperative need to identify and quantify single traffic flows. sFlow [3] is an industry standard based on statistical sampling which attempts to provide a solution to this. Due to the size of the ATLAS network, the collection and analysis of the sFlow data from all devices generates a data handling problem of its own. This paper describes how this problem is addressed by making it possible to collect and store data either centrally or distributed according to need. The methods used to present the results in a relevant fashion for system analysts are discussed and we explore the possibilities and limitations of this diagnostic tool, giving an example of its use in solving system problems that arise during the ATLAS data taking.
Monitoring individual traffic flows within the ATLAS TDAQ network
Sjoen, R; Ciobotaru, M; Batraneanu, S M; Leahu, L; Martin, B; Al-Shabibi, A
2010-01-01
The ATLAS data acquisition system consists of four different networks interconnecting up to 2000 processors using up to 200 edge switches and five multi-blade chassis devices. The architecture of the system has been described in [1] and its operational model in [2]. Classical, SNMP-based, network monitoring provides statistics on aggregate traffic, but for performance monitoring and troubleshooting purposes there was an imperative need to identify and quantify single traffic flows. sFlow [3] is an industry standard based on statistical sampling which attempts to provide a solution to this. Due to the size of the ATLAS network, the collection and analysis of the sFlow data from all devices generates a data handling problem of its own. This paper describes how this problem is addressed by making it possible to collect and store data either centrally or distributed according to need. The methods used to present the results in a relevant fashion for system analysts are discussed and we explore the possibilities a...
Internet traffic load balancing using dynamic hashing with flow volume
Jo, Ju-Yeon; Kim, Yoohwan; Chao, H. Jonathan; Merat, Francis L.
2002-07-01
Sending IP packets over multiple parallel links is in extensive use in today's Internet and its use is growing due to its scalability, reliability and cost-effectiveness. To maximize the efficiency of parallel links, load balancing is necessary among the links, but it may cause the problem of packet reordering. Since packet reordering impairs TCP performance, it is important to reduce the amount of reordering. Hashing offers a simple solution to keep the packet order by sending a flow over a unique link, but static hashing does not guarantee an even distribution of the traffic amount among the links, which could lead to packet loss under heavy load. Dynamic hashing offers some degree of load balancing but suffers from load fluctuations and excessive packet reordering. To overcome these shortcomings, we have enhanced the dynamic hashing algorithm to utilize the flow volume information in order to reassign only the appropriate flows. This new method, called dynamic hashing with flow volume (DHFV), eliminates unnecessary flow reassignments of small flows and achieves load balancing very quickly without load fluctuation by accurately predicting the amount of transferred load between the links. In this paper we provide the general framework of DHFV and address the challenges in implementing DHFV. We then introduce two algorithms of DHFV with different flow selection strategies and show their performances through simulation.
A stochastic approach to the flow-concentration curve in traffic flow theory
Qian, Wei-Liang; Lin, Kai; Siqueira, Adriano F
2016-01-01
An alternative stochastic model for the fundamental diagram of traffic flow with minimal number of parameters is proposed. The key features of the model lie in its "catastrophic" potential function as well as in its stochastic nature, which makes it possible to describe the main features of the flow-concentration relation. In particular, the inverse-$\\lambda$ shape as well as the wide scattering of congested traffic data are both reproduced. In our model, the scattering of the data is attributed to the noise terms introduced in the stochastic differential equations. The inverse-$\\lambda$ shape and the associated sudden jump of physical quantities arise, on the other hand, due to the existence of two simultaneous stable traffic flow states and/or to the effect of stochastic noises on the stability of the system. The model parameters are calibrated and compared qualitatively with the data.
Interaction Between Strategic and Local Traffic Flow Controls
Grabbe, Son; Sridhar, Banavar; Mukherjee, Avijit; Morando, Alexander
2010-01-01
The loosely coordinated sets of traffic flow management initiatives that are operationally implemented at the national- and local-levels have the potential to under, over, and inconsistently control flights. This study is designed to explore these interactions through fast-time simulations with an emphasis on identifying inequitable situations in which flights receive multiple uncoordinated delays. Two operationally derived scenarios were considered in which flights arriving into the Dallas/Fort Worth International Airport were first controlled at the national-level, either with a Ground Delay Program or a playbook reroute. These flights were subsequently controlled at the local level. The Traffic Management Advisor assigned them arrival scheduling delays. For the Ground Delay Program scenarios, between 51% and 53% of all arrivals experience both pre-departure delays from the Ground Delay Program and arrival scheduling delays from the Traffic Management Advisor. Of the subset of flights that received multiple delays, between 5.7% and 6.4% of the internal departures were first assigned a pre-departure delay by the Ground Delay Program, followed by a second pre-departure delay as a result of the arrival scheduling. For the playbook reroute scenario, Dallas/Fort Worth International Airport arrivals were first assigned pre-departure reroutes based on the MW_2_DALLAS playbook plan, and were subsequently assigned arrival scheduling delays by the Traffic Management Advisor. Since the airport was operating well below capacity when the playbook reroute was in effect, only 7% of the arrivals were observed to receive both rerouting and arrival scheduling delays. Findings from these initial experiments confirm field observations that Ground Delay Programs operated in conjunction with arrival scheduling can result in inequitable situations in which flights receive multiple uncoordinated delays.
How long will the traffic flow time series keep efficacious to forecast the future?
Yuan, PengCheng; Lin, XuXun
2017-02-01
This paper investigate how long will the historical traffic flow time series keep efficacious to forecast the future. In this frame, we collect the traffic flow time series data with different granularity at first. Then, using the modified rescaled range analysis method, we analyze the long memory property of the traffic flow time series by computing the Hurst exponent. We calculate the long-term memory cycle and test its significance. We also compare it with the maximum Lyapunov exponent method result. Our results show that both of the freeway traffic flow time series and the ground way traffic flow time series demonstrate positively correlated trend (have long-term memory property), both of their memory cycle are about 30 h. We think this study is useful for the short-term or long-term traffic flow prediction and management.
A Macro Model for Traffic Flow with Consideration of Static Bottleneck
Institute of Scientific and Technical Information of China (English)
唐铁桥; 李鹏; 吴永洪; 黄海军
2012-01-01
In this paper, we develop a macro model for traffic flow with consideration of static bottleneck to explore the impacts of static bottleneck on traffic flow. The analytical and numerical results show that the proposed model can qualitatively describe the equilibrium flux, uniform flow and small perturbation under the action of a static bottleneck.
Real-time Capturing and Measurement of Traffic Flow Based on WinPcap
Institute of Scientific and Technical Information of China (English)
HU Wen-jing; LI Ming; QIU Run-he; LIU Jin-gao
2006-01-01
In order to understand how a network is being used or whether it is being abused, an administrator needs to inspect the flow of the traffic and "infers" the intent of the users and applications. So the network traffic measurement and analysis are crucial to network monitoring, reliable DDoS detecting and attack source locating as well[1-4]. In this paper, we discuss the principle of real-time network traffic measurement and analysis through embedding a traffic measurement and analysis engine into IP packet-decoding module, and emphasize the implementation of visualizing the real-time network traffic, which are helpful to network monitoring and network traffic modeling.
Fuzzy Prediction for Traffic Flow Based on Delta Test
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Yang Wang
2016-01-01
Full Text Available This paper presents a novel approach to one-step-forward prediction of traffic flow based on fuzzy reasoning. The successful construction of a competent fuzzy inference system of Sugeno type largely relies on proper choice of input dimension and accurate estimation of structure parameters and rules. The first issue is addressed with a proposed method, based on δ-test, which can simultaneously determine input dimension and reduce noise level. In response to the second issue, two clustering techniques, based on nearest-neighbor clustering and Gaussian mixture models, are successively employed to determine the antecedent parameters and rules, and the estimation for the consequent parameters is achieved by the least square estimation technique. A number of experiments have been performed on the one-week data of traffic flow to evaluate the proposed approach in terms of denosing, prediction performances, overfitting, and so forth. The experimental results have demonstrated that the proposed prediction approach is effective in removing noise and constructing a competent and compact fuzzy inference system without significant overfitting.
Failure of classical traffic flow theories: Stochastic highway capacity and automatic driving
Kerner, Boris S.
2016-05-01
In a mini-review Kerner (2013) it has been shown that classical traffic flow theories and models failed to explain empirical traffic breakdown - a phase transition from metastable free flow to synchronized flow at highway bottlenecks. The main objective of this mini-review is to study the consequence of this failure of classical traffic-flow theories for an analysis of empirical stochastic highway capacity as well as for the effect of automatic driving vehicles and cooperative driving on traffic flow. To reach this goal, we show a deep connection between the understanding of empirical stochastic highway capacity and a reliable analysis of automatic driving vehicles in traffic flow. With the use of simulations in the framework of three-phase traffic theory, a probabilistic analysis of the effect of automatic driving vehicles on a mixture traffic flow consisting of a random distribution of automatic driving and manual driving vehicles has been made. We have found that the parameters of automatic driving vehicles can either decrease or increase the probability of the breakdown. The increase in the probability of traffic breakdown, i.e., the deterioration of the performance of the traffic system can occur already at a small percentage (about 5%) of automatic driving vehicles. The increase in the probability of traffic breakdown through automatic driving vehicles can be realized, even if any platoon of automatic driving vehicles satisfies condition for string stability.
Influence of lane change on stability analysis for two-lane traffic flow
Institute of Scientific and Technical Information of China (English)
Zheng Liang; Ma Shou-Feng; Zhong Shi-Quan
2011-01-01
This paper deals mainly with the influence of lane changing behaviours on the stability of two-lane traffic flow under a periodic boundary condition.Following the description of an optimal velocity model for two vehicle groups and the derivation of their stability conditions,the feedback signals,which involve information about vehicles from both lanes acting on the two-lane traffic system,are introduced into the optimal velocity model.The control signals play a role in alleviating the traffic jam only if the traffic state is in congestion,and their role will vanish if the traffic state is in the steady state.The numerical simulations show that lane changing behaviours can break the steady state of two-lane traffic flow and aggravate the traffic disturbance,but the control method would successfully suppress the traffic jam eventually,which implies that the conclusions obtained here have certain theoretical and practical significance.
Dynamic route guidance strategy in a two-route pedestrian-vehicle mixed traffic flow system
Liu, Mianfang; Xiong, Shengwu; Li, Bixiang
2016-05-01
With the rapid development of transportation, traffic questions have become the major issue for social, economic and environmental aspects. Especially, during serious emergencies, it is very important to alleviate road traffic congestion and improve the efficiency of evacuation to reduce casualties, and addressing these problems has been a major task for the agencies responsible in recent decades. Advanced road guidance strategies have been developed for homogeneous traffic flows, or to reduce traffic congestion and enhance the road capacity in a symmetric two-route scenario. However, feedback strategies have rarely been considered for pedestrian-vehicle mixed traffic flows with variable velocities and sizes in an asymmetric multi-route traffic system, which is a common phenomenon in many developing countries. In this study, we propose a weighted road occupancy feedback strategy (WROFS) for pedestrian-vehicle mixed traffic flows, which considers the system equilibrium to ease traffic congestion. In order to more realistic simulating the behavior of mixed traffic objects, the paper adopted a refined and dynamic cellular automaton model (RDPV_CA model) as the update mechanism for pedestrian-vehicle mixed traffic flow. Moreover, a bounded rational threshold control was introduced into the feedback strategy to avoid some negative effect of delayed information and reduce. Based on comparisons with the two previously proposed strategies, the simulation results obtained in a pedestrian-vehicle traffic flow scenario demonstrated that the proposed strategy with a bounded rational threshold was more effective and system equilibrium, system stability were reached.
2012-01-24
...-ready technologies and innovative operational approaches for managing traffic congestion within the... No: 2012-1321] DEPARTMENT OF TRANSPORTATION Meeting and Webinar on the Active Traffic and Demand... Traffic and Demand Management (ADTM) and Intelligent Network Flow Optimization (INFLO)...
Treiber, Martin; Kesting, Arne; Helbing, Dirk
2006-07-01
We investigate the adaptation of the time headways in car-following models as a function of the local velocity variance, which is a measure of the inhomogeneity of traffic flow. We apply this mechanism to several car-following models and simulate traffic breakdowns in open systems with an on-ramp as bottleneck and in a closed ring road. Single-vehicle data and one-minute aggregated data generated by several virtual detectors show a semiquantitative agreement with microscopic and flow-density data from the Dutch freeway A9. This includes the observed distributions of the net time headways for free and congested traffic, the velocity variance as a function of density, and the fundamental diagram. The modal value of the time headway distribution is shifted by a factor of about 2 under congested conditions. Macroscopically, this corresponds to the capacity drop at the transition from free to congested traffic. The simulated fundamental diagram shows free, synchronized, and jammed traffic, and a wide scattering in the congested traffic regime. We explain this by a self-organized variance-driven process that leads to the spontaneous formation and decay of long-lived platoons even for a deterministic dynamics on a single lane.
Adaptive Resource Allocation and Internet Traffic Engineering on Data Network
Directory of Open Access Journals (Sweden)
Hatim Hussein
2015-02-01
Full Text Available This research paper describes the issues of bandwid th allocation, optimum capacity allocation, network operational cost reduction, and improve Int ernet user experience. Traffic engineering (TE is used to manipulate network traffic to achie ve certain requirements and meets certain needs. TE becomes one of the most important buildin g blocks in the design of the Internet backbone infrastructure. Research objective: effici ent allocation of bandwidth across multiple paths. Optimum path selection. Minimize network tra ffic delays and maximize bandwidth utilization over multiple network paths. The bandwi dth allocation is performed proportionally over multiple paths based on the path capacity.
Effects of speed bottleneck on traffic flow with feedback control signal
Zhu, Kangli; Bi, Jiantao; Wu, Jianjun; Li, Shubin
2016-09-01
Various car-following models (CMs) have been developed to capture the complex characteristics of microscopic traffic flow, among which the coupled map CM can better reveal and reflect various phenomena of practical traffic flow. Capacity change at bottleneck contributes to high-density traffic flow upstream the bottleneck and contains very complex dynamic behavior. In this paper, we analyze the effect of speed bottleneck on the spatial-temporal evolution characteristics of traffic flow, and propose a method to reduce traffic congestion with the feedback control signal based on CM. Simulation results highlight the potential of using the feedback signal to control the stop-and-go wave and furthermore to alleviate the traffic congestion effectively.
Institute of Scientific and Technical Information of China (English)
YOU Qin; ZHAO Ying-cai; LI Chun-hao; LIU Guo-liang
2004-01-01
The calculating method of Self-Adaptive Forecasting Method (SAFM) is stated in this paper, which is also used in forecasting Total Telecommunication Service Traffic (TTST). It has the advantage that weight selection can be self-adaptive so that it can get better forecasting value compared with the Moving Average Method (MAM) and the Exponential Smoothing Method (ESM).
Li, Qi-Lang; Wong, S. C.; Min, Jie; Tian, Shuo; Wang, Bing-Hong
2016-08-01
This study examines the cellular automata traffic flow model, which considers the heterogeneity of vehicle acceleration and the delay probability of vehicles. Computer simulations are used to identify three typical phases in the model: free-flow, synchronized flow, and wide moving traffic jam. In the synchronized flow region of the fundamental diagram, the low and high velocity vehicles compete with each other and play an important role in the evolution of the system. The analysis shows that there are two types of bistable phases. However, in the original Nagel and Schreckenberg cellular automata traffic model, there are only two kinds of traffic conditions, namely, free-flow and traffic jams. The synchronized flow phase and bistable phase have not been found.
Analysis of CO2 emission in traffic flow and numerical tests
Zhu, Wen-Xing
2013-10-01
We investigated the carbon dioxide emission rate in traffic flow analytically and numerically. The emission model was derived based on Bando’s optimal velocity model with a consideration of slope. Simulations were conducted to examine the relationship between the CO2 emission rate of vehicles and slope of road, traffic density, and road length. Analysis of the results shows that some original laws of CO2 emission in traffic flow with congestion were exhibited.
Jin–Xin relaxation method for solving a traffic flow problem in one dimension
Ambar Sulistiyawati, Bernadetta; Mungkasi, Sudi
2017-01-01
We test the performance of the Jin–Xin relaxation and Lax–Friedrichs finite volume numerical methods in solving a traffic flow problem. In particular, we focus on traffic flow at a traffic light turning from red to green. Numerical solutions are compared with the analytical solution to the mathematical model. We find that the Jin–Xin relaxation solution is more accurate than the Lax–Friedrichs finite volume solution.
Lane changing analysis for two-lane traffic flow
Institute of Scientific and Technical Information of China (English)
Tieqiao Tang; Haijun Huang; S.C.Wong; Rui Jiang
2007-01-01
In this paper,the two-lane traffic are studiedby using the lane-changing rules in the car-followingmodels.The simulation show that the frequent lanechanging occurs when the lateral distance in car fol-lowing activities is considered and it gives rise to oscil-lating waves.In contrast,if the lateral distance is notconsidered (or considered occasionally),the lane chang-ing appears infrequently and soliton waves occurs.Thisimplies that the stabilization mechanism no longer func-tions when the lane changing is permitted.Since theoscillating and soliton waves correspond to the unsta-ble and metastable flow regimes,respectively,our studyverifies that a phase transition may occur as a result ofthe lane changing.
The effect of lateral interaction on traffic flow
Bouadi, M.; Jetto, K.; Benyoussef, A.; Kenz, A.
2016-10-01
We propose an extended cellular automaton model for traffic flow, taking into account lateral interactions with defects and between vehicles. The fundamental diagram for a given defects density on the road is studied. It is found that the plateau size increases linearly with the decreasing road width for little defects densities. Furthermore, the capacity increases linearly with the increasing road width. However, for a fixed road width, the capacity decreases exponentially with the increasing defects density. The lateral effects for non-mutual interactions between lanes and for the same maximal velocity is also investigated. It is found that the lateral effects on one lane are meaningful only when the density on the other lane is above the critical density. However, the lateral effects are always present if fast and slow lanes exist. Little differences have been found for the mutual interactions.
An Adaptive Service Platform for Traffic Management and Surveillance
Sapkota, Brahmananda; Sinderen, van Marten
2011-01-01
The increasing number of road vehicles has given rise to increasingly adverse consequences in the society. Some of the major concerns that arise due to such an increase in road vehicles are: safety of the people using the road, cost and efficiency of the traffic management and the environmental foot
Big Data-Driven Based Real-Time Traffic Flow State Identification and Prediction
Directory of Open Access Journals (Sweden)
Hua-pu Lu
2015-01-01
Full Text Available With the rapid development of urban informatization, the era of big data is coming. To satisfy the demand of traffic congestion early warning, this paper studies the method of real-time traffic flow state identification and prediction based on big data-driven theory. Traffic big data holds several characteristics, such as temporal correlation, spatial correlation, historical correlation, and multistate. Traffic flow state quantification, the basis of traffic flow state identification, is achieved by a SAGA-FCM (simulated annealing genetic algorithm based fuzzy c-means based traffic clustering model. Considering simple calculation and predictive accuracy, a bilevel optimization model for regional traffic flow correlation analysis is established to predict traffic flow parameters based on temporal-spatial-historical correlation. A two-stage model for correction coefficients optimization is put forward to simplify the bilevel optimization model. The first stage model is built to calculate the number of temporal-spatial-historical correlation variables. The second stage model is present to calculate basic model formulation of regional traffic flow correlation. A case study based on a real-world road network in Beijing, China, is implemented to test the efficiency and applicability of the proposed modeling and computing methods.
Multi-Dimensional Traffic Flow Time Series Analysis with Self-Organizing Maps
Institute of Scientific and Technical Information of China (English)
CHEN Yudong; ZHANG Yi; HU Jianming
2008-01-01
The two important features of self-organizing maps (SOM), topological preservation and easy visualization, give it great potential for analyzing multi-dimensional time series, specifically traffic flow time series in an urban traffic network. This paper investigates the application of SOM in the representation and prediction of multi-dimensional traffic time series. First, SOMs are applied to cluster the time series and to project each multi-dimensional vector onto a two-dimensional SOM plane while preserving the topological relationships of the original data. Then, the easy visualization of the SOMs is utilized and several explora-tory methods are used to investigate the physical meaning of the clusters as well as how the traffic flow vec-tors evolve with time. Finally, the k-nearest neighbor (kNN) algorithm is applied to the clustering result to perform short-term predictions of the traffic flow vectors. Analysis of real world traffic data shows the effec-tiveness of these methods for traffic flow predictions, for they can capture the nonlinear information of traffic flows data and predict traffic flows on multiple links simultaneously.
Multi-class continuum traffic flow models: Analysis and simulation methods
Van Wageningen-Kessels, F.L.M.
2013-01-01
How to model and simulate traffic flow including different vehicles such as cars and trucks? This dissertation answers this question by analyzing existing models and simulation methods and by developing new ones. The new model (Fastlane) describes traffic as a continuum flow while accounting for dif
Adaptive Traffic Continuum Model%适应性交通流连续性模型
Institute of Scientific and Technical Information of China (English)
夏玉显; 薛郁; 梁玉娟
2015-01-01
【目的】考虑人的主动行为在复杂的交通系统所起的作用，从微观机理出发，利用气体动理学理论建立交通流连续性宏观模型，研究交通的拥堵现象。【方法】假定单一司机的期望速度与其局域瞬时速度成正比，考虑司机期望速度随时间的驰豫变化，利用广义 Paveri-Fontana 等式，通过运用距方程和 Chapman-Enskog 方法，导出类 Naveri-Stokes 方程的适应性交通流模型；然后对适应性交通流模型进行线性稳定性分析，并通过数值分析验证适应性模型的合理性。【结果】适应性模型能更好地解释高密度下的时停时走交通现象，描述交通堵塞的消散过程，反映右转车流的“挤压”效应。【结论】引入司机的期望速度的宏观交通流动力学方程能较好模拟高密度的交通拥堵现象。%Objective]The congestion of traffic flow is studied by establishing kinetic models from microscopic model to macroscopic one.[Methods]Considering that the desired velocity of a single driver changes with the surrounding and is related to local instantaneous velocity of the vehicle in real traffic,the desired velocity is assumed to be proportional to the local instantane-ous velocity.The adaptive flux model like Navier-Stokes traffic equation is derived from the ex-tended Paveri-Fontana equation.The steady condition of the model is obtained by the linear sta-bility analysis.[Results]Compared with steady condition of both Kerner-Konhäuser model and Helbing model,it is found that the adaptive model has the ability to illustrate stop-and-go traf-fic in middle-high density.Numerical solution of the macroscopic traffic equations verifies rationality of our model.[Conclusion]The hydro-dynamic traffic model is suitable to simulate the congestion phenomena in middle-high density via introducing the desired velocity of driver.
An Improved Car-Following Model for Multiphase Vehicular Traffic Flow and Numerical Tests
Li, Zhi-Peng; Gong, Xiao-Bo; Liu, Yun-Cai
2006-08-01
This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The improvement of this model over the previous one lies in that it performs more realistically in the dynamical motion for small delay time. The traffic behavior of the improved model is investigated with analytic and numerical methods with the finding that the new consideration could further stabilize traffic flow. And some simulation tests verify that the proposed model can demonstrate some complex physical features observed recently in real traffic such as the existence of three phases: free flow, coexisting flow, and jam flow; spontaneous formation of density waves; sudden flow drop in flow-density plane; traffic hysteresis in transition between the free and the coexisting flow. Furthermore, the improved model also predicts that the stable state to relative density in the coexisting flow is insusceptible to noise.
An Improved Car-Following Model for Multiphase Vehicular Traffic Flow and Numerical Tests
Institute of Scientific and Technical Information of China (English)
LI Zhi-Peng; GONG Xiao-Bo; LIU Yun-Cai
2006-01-01
This paper attempts to introduce an improved difference model that modifies a car-following model, which takes the next-nearest-neighbor interaction into account. The improvement of this modelover the previous one lies in that it performs more realistically in the dynamical motion for small delay time. The traffic behavior of the improved model is investigated with analytic and numerical methods with the finding that the new consideration could further stabilize traffic flow. And some simulation tests verify that the proposed model can demonstrate some complex physical features observed recently in real traffic such as the existence of three phases: free flow, coexisting flow, and jam flow;spontaneous formation of density waves; sudden flow drop in flow-density plane; traffic hysteresis in transition between the free and the coexisting flow. Furthermore, the improved model also predicts that the stable state to relative density in the coexisting flow is insusceptible to noise.
Adaptive radio resource allocation for multiple traffic OFDMA broadband wireless access system
Institute of Scientific and Technical Information of China (English)
LU Yan-hui; LUO Tao; YIN Chang-chuan; YUE Guang-xin
2006-01-01
In this article, an adaptive radio resource allocation algorithm applied to multiple traffic orthogonal frequency division multiple access (OFDMA) system is proposed, which distributes subcarriers and bits among users according to their different quality of service requirements and traffic type. By classifying and prioritizing the users based on their traffic characteristic and ensuring resource for higher priority users, the new scheme decreases tremendously the outage probability of the users requiting a real-time transmission without impact on the spectrum efficiency of system, as well as the outage probability of data users is not increased compared with the radio resource allocation methods published.
Video-based measurement and data analysis of traffic flow on urban expressways
Institute of Scientific and Technical Information of China (English)
Xian-Qing Zheng; Zheng Wu; Shi-Xiong Xu; Ming-Min Guo; Zhan-Xi Lin; Ying-Ying Zhang
2011-01-01
A new video-based measurement is proposed to collect and investigate traffic flow parameters.The output of the measurement is velocity-headway distance data pairs.Because density can be directly acquired by the reciprocal of headway distance, the data pairs have the advantage of better simultaneity than those from common detectors.By now,over 33 000 pairs of data have been collected from two road sections in the cities of Shanghai and Zhengzhou.Through analyzing the video files recording traffic movements on urban expressways, the following issues are studied: laws of vehicle velocity changing with headway distance, proportions of different driving behaviors in the traffic system, and characteristics of traffic flow in snowy days.The results show that the real road traffic is very complex, and factors such as location and climate need to be taken into consideration in the formation of traffic flow models.
Fundamental diagram in traffic flow of mixed vehicles on multi-lane highway
Tanaka, Katsunori; Nagatani, Takashi; Masukura, Shuichi
2008-09-01
We study the fundamental diagram for traffic flow of vehicular mixture on a multi-lane highway. We present the car-following model of multi-lane traffic in which slow and fast vehicles flow with changing lanes. We investigate the traffic states of the vehicular mixture under the periodic boundary. Two values of the current appear at a density and two current curves are obtained. Vehicles move with changing lanes in the traffic state of high current, while vehicles move without changing lanes in the traffic state of low current. They depend on the density, the fraction of slow vehicles, and the initial condition. In the high-current curve, the jamming transition between the free flow and the jammed state occurs at a low density. The fundamental diagrams (current-density diagrams) are shown for the single-lane, two-lane, three-lane, and four-lane traffics.
Performance Evaluation of Adaptive Rate Control (ARC for Burst Traffic over ATM Network
Directory of Open Access Journals (Sweden)
V.Ramesh
2010-01-01
Full Text Available Many research works have already been done for congestion control and resource management in ATM networks using static and dynamic algorithms. However, no comprehensive scheme has been suggested, which can claim optimized the resource allocations fulfilling the requirements of quality of services (QoS for existing and incoming sources. The paper suggests a new approach, which would make the dynamic allocation of resources by controlling the input rate (l, output/server rate (m and buffer size (c individually or in conjunction. The newly proposed approach with dynamical allocation of resources is much more comprehensive in nature and claims a shorter convergence time than the other previously suggested schemes based on similar dynamic allocation principle. In this paper we describe an Adaptive Rate Control (ARC implemented to improve the performance of high-speed network to handle burst traffic by guaranteeing the cell loss ratio (CLR for all cell streams. First, the cases in which a Tahoe, Reno, New Reno, SACK and Plain schemes are applicable in peak-cell-rate (PCR are discussed. The ARC improves the performance by regulating the increment (up and the decrease (down of window size (flow control. Incoming traffic rate, number of cell drop, preset size of the window and estimated delay time are taken into account for this regulation. Simulations are used to investigate how Tahoe, Reno, New Reno, SACK and Plain can conduct, as congestion existed. Then we compare these results from four schemes to the “Plain” scheme (no flow control application and to the proposed ARC. By altering windows size for the mentioned six schemes, we can obtain the supportive results.
Analysis of ETMS Data Quality for Traffic Flow Management Decisions
Chatterji, Gano B.; Sridhar, Banavar; Kim, Douglas
2003-01-01
The data needed for air traffic flow management decision support tools is provided by the Enhanced Traffic Management System (ETMS). This includes both the tools that are in current use and the ones being developed for future deployment. Since the quality of decision support provided by all these tools will be influenced by the quality of the input ETMS data, an assessment of ETMS data quality is needed. Motivated by this desire, ETMS data quality is examined in this paper in terms of the unavailability of flight plans, deviation from the filed flight plans, departure delays, altitude errors and track data drops. Although many of these data quality issues are not new, little is known about their extent. A goal of this paper is to document the magnitude of data quality issues supported by numerical analysis of ETMS data. Guided by this goal, ETMS data for a 24-hour period were processed to determine the number of aircraft with missing flight plan messages at any given instant of time. Results are presented for aircraft above 18,000 feet altitude and also at all altitudes. Since deviation from filed flight plan is also a major cause of trajectory-modeling errors, statistics of deviations are presented. Errors in proposed departure times and ETMS-generated vertical profiles are also shown. A method for conditioning the vertical profiles for improving demand prediction accuracy is described. Graphs of actual sector counts obtained using these vertical profiles are compared with those obtained using the Host data for sectors in the Fort Worth Center to demonstrate the benefit of preprocessing. Finally, results are presented to quantify the extent of data drops. A method for propagating track positions during ETMS data drops is also described.
Dynamics of Motorized Vehicle Flow under Mixed Traffic Circumstance*
Institute of Scientific and Technical Information of China (English)
GUO nong-Wei; GAO Zi-You; ZHAO Xiao-Mei; XIE Dong-Fan
2011-01-01
To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed.Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles.By numerical simulations, the flux-density relation, the temporal-spatial dynamics, and the velocity evolution are investigated in detail.The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13％.Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low.Moreover, non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle densityincreases.The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.
Modeling Mixed Traffic Flow at Crosswalks in Micro-Simulations Using Cellular Automata
Institute of Scientific and Technical Information of China (English)
DUAN Houli; ZHANG Yi
2007-01-01
The cellular automata (CA) micro-simulation model was used to describe the behavior of the mixed traffic flows at crosswalks where the pedestrians compete with the vehicles to cross the roadway. The focus of this paper is the behavior of pedestrians and the influence of pedestrians' behavior on the vehicle flow, pedestrian flows, and the vehicle waiting time. The proportion of pedestrians who do not obey traffic laws, the group effect, and expected waiting time of pedestrians, regarded as the most important pedestrian characteristics, are taken into consideration in the analysis. Simulation results show the ability of the microsimulation to capture the most important features of mixed traffic flow.
Detecting Anomaly in Traffic Flow from Road Similarity Analysis
Liu, Xinran
2016-06-02
Taxies equipped with GPS devices are considered as 24-hour moving sensors widely distributed in urban road networks. Plenty of accurate and realtime trajectories of taxi are recorded by GPS devices and are commonly studied for understanding traffic dynamics. This paper focuses on anomaly detection in traffic volume, especially the non-recurrent traffic anomaly caused by unexpected or transient incidents, such as traffic accidents, celebrations and disasters. It is important to detect such sharp changes of traffic status for sensing abnormal events and planning their impact on the smooth volume of traffic. Unlike existing anomaly detection approaches that mainly monitor the derivation of current traffic status from history in the past, the proposed method in this paper evaluates the abnormal score of traffic on one road by comparing its current traffic volume with not only its historical data but also its neighbors. We define the neighbors as the roads that are close in sense of both geo-location and traffic patterns, which are extracted by matrix factorization. The evaluation results on trajectories data of 12,286 taxies over four weeks in Beijing show that our approach outperforms other baseline methods with higher precision and recall.
CONTROLLING TRAFFIC FLOW IN MULTILANE-ISOLATED INTERSECTION USING ANFIS APPROACH TECHNIQUES
Directory of Open Access Journals (Sweden)
G. R. LAI
2015-08-01
Full Text Available Many controllers have applied the Adaptive Neural-Fuzzy Inference System (ANFIS concept for optimizing the controller performance. However, there are less traffic signal controllers developed using the ANFIS concept. ANFIS traffic signal controller with its fuzzy rule base and its ability to learn from a set of sample data could improve the performance of Existing traffic signal controlling system to reduce traffic congestions at most of the busy traffic intersections in city such as Kuala Lumpur, Malaysia. The aim of this research is to develop an ANFIS traffic signals controller for multilane-isolated four approaches intersections in order to ease traffic congestions at traffic intersections. The new concept to generate sample data for ANFIS training is introduced in this research. The sample data is generated based on fuzzy rules and can be analysed using tree diagram. This controller is simulated on multilane-isolated traffic intersection model developed using M/M/1 queuing theory and its performance in terms of average waiting time, queue length and delay time are compared with traditional controllers and fuzzy controller. Simulation result shows that the average waiting time, queue length, and delay time of ANFIS traffic signal controller are the lowest as compared to the other three controllers. In conclusion, the efficiency and performance of ANFIS controller are much better than that of fuzzy and traditional controllers in different traffic volumes.
Delay-feedback control strategy for reducing CO2 emission of traffic flow system
Zhang, Li-Dong; Zhu, Wen-Xing
2015-06-01
To study the signal control strategy for reducing traffic emission theoretically, we first presented a kind of discrete traffic flow model with relative speed term based on traditional coupled map car-following model. In the model, the relative speed difference between two successive running cars is incorporated into following vehicle's acceleration running equation. Then we analyzed its stability condition with discrete control system stability theory. Third, we designed a delay-feedback controller to suppress traffic jam and decrease traffic emission based on modern controller theory. Last, numerical simulations are made to support our theoretical results, including the comparison of models' stability analysis, the influence of model type and signal control on CO2 emissions. The results show that the temporal behavior of our model is superior to other models, and the traffic signal controller has good effect on traffic jam suppression and traffic CO2 emission, which fully supports the theoretical conclusions.
Car Delay Model near Bus Stops with Mixed Traffic Flow
Yang Xiaobao; Huan Mei; Gao Ziyou
2013-01-01
This paper proposes a model for estimating car delays at bus stops under mixed traffic using probability theory and queuing theory. The roadway is divided to serve motorized and nonmotorized traffic streams. Bus stops are located on the nonmotorized lanes. When buses dwell at the stop, they block the bicycles. Thus, two conflict points between car stream and other traffic stream are identified. The first conflict point occurs as bicycles merge to the motorized lane to avoid waiting behind the...
Woo, Seok; Kim, Kiseon
In this paper, we propose an adaptive power controlled MAC protocol with a traffic-aware scheme specifically designed to reduce both energy and latency in wireless sensor networks. Typically, existing MAC protocols for sensor networks sacrifice latency performance for node energy efficiency. However, some sensor applications for emergencies require rather fast transmissions of sensed data, where we need to consider both energy and latency together. The proposed MAC protocol includes two novel ideas: one is a transmission power control scheme for improving latency in high traffic loads, and the other is a traffic-aware scheme to save more energy in low traffic loads. The transmission power control scheme increases channel utilization by mitigating interference between nodes, and the traffic-aware scheme allows nodes to sleep to reduce idle energy consumption when there are no traffic loads in a network. Simulation results show that the proposed protocol significantly reduces the latency as well as the energy consumption compared to the S-MAC protocol specifically for a large transmission power of nodes and low network traffic.
Cellular automata model for urban road traffic flow considering pedestrian crossing street
Zhao, Han-Tao; Yang, Shuo; Chen, Xiao-Xu
2016-11-01
In order to analyze the effect of pedestrians' crossing street on vehicle flows, we investigated traffic characteristics of vehicles and pedestrians. Based on that, rules of lane changing, acceleration, deceleration, randomization and update are modified. Then we established two urban two-lane cellular automata models of traffic flow, one of which is about sections with non-signalized crosswalk and the other is on uncontrolled sections with pedestrians crossing street at random. MATLAB is used for numerical simulation of the different traffic conditions; meanwhile space-time diagram and relational graphs of traffic flow parameters are generated and then comparatively analyzed. Simulation results indicate that when vehicle density is lower than around 25 vehs/(km lane), pedestrians have modest impact on traffic flow, whereas when vehicle density is higher than about 60 vehs/(km lane), traffic speed and volume will decrease significantly especially on sections with non-signal-controlled crosswalk. The results illustrate that the proposed models reconstruct the traffic flow's characteristic with the situation where there are pedestrians crossing and can provide some practical reference for urban traffic management.
Efficient algorithms for optimal arrival scheduling and air traffic flow management
Saraf, Aditya
search for optimal trajectories to be flown by each aircraft so that the flows commanded by the outer control-module are achieved. The two-level control system is tested in a dynamic simulation. Furthermore, as a component of the Eulerian part of this two-level system, we present a method for deriving an aggregate airspace-model in real-time, without depending on online integration of aircraft trajectories. This method uses a baseline Eulerian airspace-model, which is derived offline using historical track-data. In real-time, parameters of this model are adapted depending on the differences between the baseline-model and the real-world. This book-keeping based model-derivation indirectly retains some trajectory information. Hence, it serves as an excellent trade-off between Eulerian and trajectory-based modeling approaches. Most importantly, as a vital improvement over previous approaches, we take into consideration the control-dependent nature of the Eulerian-model while computing optimal flow-control decisions. As a proof of concept, we derive a baseline model for the Fort-Worth center and adapt it to predict sector-counts for another set of air traffic data. We also demonstrate the use of this model in a simulation-based optimization scheme for regulating the arrival flow at the Dallas Fort-Worth airport. An application to optimal re-routing strategy computation is also presented.
Relationship between microscopic dynamics in traffic flow and complexity in networks.
Li, Xin-Gang; Gao, Zi-You; Li, Ke-Ping; Zhao, Xiao-Mei
2007-07-01
Complex networks are constructed in the evolution process of traffic flow, and the states of traffic flow are represented by nodes in the network. The traffic dynamics can then be studied by investigating the statistical properties of those networks. According to Kerner's three-phase theory, there are two different phases in congested traffic, synchronized flow and wide moving jam. In the framework of this theory, we study different properties of synchronized flow and moving jam in relation to complex network. Scale-free network is constructed in stop-and-go traffic, i.e., a sequence of moving jams [Chin. Phys. Lett. 10, 2711 (2005)]. In this work, the networks generated in synchronized flow are investigated in detail. Simulation results show that the degree distribution of the networks constructed in synchronized flow has two power law regions, so the distinction in topological structure can really reflect the different dynamics in traffic flow. Furthermore, the real traffic data are investigated by this method, and the results are consistent with the simulations.
Failure of classical traffic flow theories: Stochastic highway capacity and automatic driving
Kerner, Boris S
2016-01-01
In a mini-review [Physica A {\\bf 392} (2013) 5261--5282] it has been shown that classical traffic flow theories and models failed to explain empirical traffic breakdown -- a phase transition from metastable free flow to synchronized flow at highway bottlenecks. The main objective of this mini-review is to study the consequence of this failure of classical traffic-flow theories for an analysis of empirical stochastic highway capacity as well as for the effect of automatic driving vehicles and cooperative driving on traffic flow. To reach this goal, we show a deep connection between the understanding of empirical stochastic highway capacity and a reliable analysis of automatic driving vehicles in traffic flow. With the use of simulations in the framework of three-phase traffic theory, a probabilistic analysis of the effect of automatic driving vehicles on a mixture traffic flow consisting of a random distribution of automatic driving and manual driving vehicles has been made. We have found that the parameters o...
Directory of Open Access Journals (Sweden)
Lun-Hui Xu
2013-01-01
Full Text Available Urban traffic self-adaptive control problem is dynamic and uncertain, so the states of traffic environment are hard to be observed. Efficient agent which controls a single intersection can be discovered automatically via multiagent reinforcement learning. However, in the majority of the previous works on this approach, each agent needed perfect observed information when interacting with the environment and learned individually with less efficient coordination. This study casts traffic self-adaptive control as a multiagent Markov game problem. The design employs traffic signal control agent (TSCA for each signalized intersection that coordinates with neighboring TSCAs. A mathematical model for TSCAs’ interaction is built based on nonzero-sum markov game which has been applied to let TSCAs learn how to cooperate. A multiagent Markov game reinforcement learning approach is constructed on the basis of single-agent Q-learning. This method lets each TSCA learn to update its Q-values under the joint actions and imperfect information. The convergence of the proposed algorithm is analyzed theoretically. The simulation results show that the proposed method is convergent and effective in realistic traffic self-adaptive control setting.
Probabilistic Description of Traffic Breakdowns Caused by On-ramp Flow
Kuhne, Reinhart; Lubashevsky, Ihor; Mahnke, Reinhard; Kaupush, Jevgenijs
2004-01-01
The characteristic features of traffic breakdown near on-ramp are analyzed. To describe this phenomenon the probabilistic description regarding the jam emergence as the formation of a large car cluster on highway inside the synchronized traffic is constructed. In these terms the breakdown occurs through the formation of a certain critical nucleus in the metastable vehicle flow, which is located near the on-ramp. The strong cooperative car interaction in the synchronized traffic enables us to ...
Ma, Xiao; Zheng, Wei-Fan; Jiang, Bao-Shan; Zhang, Ji-Ye
2016-10-01
With the development of traffic systems, some issues such as traffic jams become more and more serious. Efficient traffic flow theory is needed to guide the overall controlling, organizing and management of traffic systems. On the basis of the cellular automata model and the traffic flow model with look-ahead potential, a new cellular automata traffic flow model with negative exponential weighted look-ahead potential is presented in this paper. By introducing the negative exponential weighting coefficient into the look-ahead potential and endowing the potential of vehicles closer to the driver with a greater coefficient, the modeling process is more suitable for the driver’s random decision-making process which is based on the traffic environment that the driver is facing. The fundamental diagrams for different weighting parameters are obtained by using numerical simulations which show that the negative exponential weighting coefficient has an obvious effect on high density traffic flux. The complex high density non-linear traffic behavior is also reproduced by numerical simulations. Project supported by the National Natural Science Foundation of China (Grant Nos. 11572264, 11172247, 11402214, and 61373009).
Heterogeneous traffic flow modelling using second-order macroscopic continuum model
Mohan, Ranju; Ramadurai, Gitakrishnan
2017-01-01
Modelling heterogeneous traffic flow lacking in lane discipline is one of the emerging research areas in the past few years. The two main challenges in modelling are: capturing the effect of varying size of vehicles, and the lack in lane discipline, both of which together lead to the 'gap filling' behaviour of vehicles. The same section length of the road can be occupied by different types of vehicles at the same time, and the conventional measure of traffic concentration, density (vehicles per lane per unit length), is not a good measure for heterogeneous traffic modelling. First aim of this paper is to have a parsimonious model of heterogeneous traffic that can capture the unique phenomena of gap filling. Second aim is to emphasize the suitability of higher-order models for modelling heterogeneous traffic. Third, the paper aims to suggest area occupancy as concentration measure of heterogeneous traffic lacking in lane discipline. The above mentioned two main challenges of heterogeneous traffic flow are addressed by extending an existing second-order continuum model of traffic flow, using area occupancy for traffic concentration instead of density. The extended model is calibrated and validated with field data from an arterial road in Chennai city, and the results are compared with those from few existing generalized multi-class models.
Craen, S. de Twisk, D.A.M. Hagenzieker, M.P. Elffers, H. & Brookhuis, K.A.
2008-01-01
To monitor novice driver performance in the first years of solo driving, a test aimed at assessing speed adaptation to the traffic situation was developed and evaluated. The Adaptation Test consisted of 18 traffic scenes presented in two (almost) identical photographs, which differed in one single d
Properties of train traffic flow in a moving block system
Institute of Scientific and Technical Information of China (English)
Wang Min; Zeng Jun-Wei; Qian Yong-Sheng; Li Wen-Jun; Yang Fang; Jia Xin-Xin
2012-01-01
The development direction of railways is toward the improvement of capacity and service quality,where the service quality includes safety,schedule,high speed,and comfort.In light of the existing cellular automaton models,in this paper,we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system.In the proposed model,we establish some sound rules to control the running processes of a train,where the rules include the departure rules in the intermediate stations,the overtaking rules,and the conditions of speed limitation for a train stopping at a station or passing through a station.With the consideration of the mixed ratio and the distance between two adjacent stations,the properties of the train traffic flow (including capacity and average speed) are simulated.The numerical results show that the interactions among different trains will affect the capacity,and a proper increase of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block.
Dynamic aggregation of traffic flows in SDN Applied to backhaul networks
DEFF Research Database (Denmark)
Kentis, Angelos Mimidis; Caba, Cosmin Marius; Soler, José
2016-01-01
or they can support a very limited number of OF rules. One way to cope with this limitation, is to perform the same logic but with fewer OF rules in the devices. As a demonstration of this operational strategy, the current paper proposes a service for traffic flow aggregation which reduces the number...... of OF rules needed in the network devices, without impacting the control plane logic. The proposed traffic flow aggregation service is tested on a set of topologies specific to the backhaul network, since they aggregate a large amount of traffic flows. The results illustrate significant reductions...
Zuurbier, F.S.; Hegyi, A.; Hoogendoorn, S.P.
2010-01-01
Marginal costs in traffic networks are the extra costs incurred to the system as the result of extra traffic. Marginal costs are required frequently e.g. when considering system optimal traffic assignment or tolling problems. When explicitly considering spillback in a traffic flow model, one can use
Traffic Flow at Sags: Theory, Modeling and Control
Goni-Ros, B.
2016-01-01
Sag vertical curves (sags) are roadway sections along which the gradient increases gradually in the direction of traffic. Empirical observations show that, on freeways, traffic congestion often occurs at sags; actually, in some countries (e.g., Japan), sags are one of the most common types of freewa
A SPATIOTEMPORAL APPROACH FOR HIGH RESOLUTION TRAFFIC FLOW IMPUTATION
Energy Technology Data Exchange (ETDEWEB)
Han, Lee [University of Tennessee, Knoxville (UTK); Chin, Shih-Miao [ORNL; Hwang, Ho-Ling [ORNL
2016-01-01
Along with the rapid development of Intelligent Transportation Systems (ITS), traffic data collection technologies have been evolving dramatically. The emergence of innovative data collection technologies such as Remote Traffic Microwave Sensor (RTMS), Bluetooth sensor, GPS-based Floating Car method, automated license plate recognition (ALPR) (1), etc., creates an explosion of traffic data, which brings transportation engineering into the new era of Big Data. However, despite the advance of technologies, the missing data issue is still inevitable and has posed great challenges for research such as traffic forecasting, real-time incident detection and management, dynamic route guidance, and massive evacuation optimization, because the degree of success of these endeavors depends on the timely availability of relatively complete and reasonably accurate traffic data. A thorough literature review suggests most current imputation models, if not all, focus largely on the temporal nature of the traffic data and fail to consider the fact that traffic stream characteristics at a certain location are closely related to those at neighboring locations and utilize these correlations for data imputation. To this end, this paper presents a Kriging based spatiotemporal data imputation approach that is able to fully utilize the spatiotemporal information underlying in traffic data. Imputation performance of the proposed approach was tested using simulated scenarios and achieved stable imputation accuracy. Moreover, the proposed Kriging imputation model is more flexible compared to current models.
Finite size scaling analysis on Nagel-Schreckenberg model for traffic flow
Balouchi, Ashkan; Browne, Dana
2015-03-01
The traffic flow problem as a many-particle non-equilibrium system has caught the interest of physicists for decades. Understanding the traffic flow properties and though obtaining the ability to control the transition from the free-flow phase to the jammed phase plays a critical role in the future world of urging self-driven cars technology. We have studied phase transitions in one-lane traffic flow through the mean velocity, distributions of car spacing, dynamic susceptibility and jam persistence -as candidates for an order parameter- using the Nagel-Schreckenberg model to simulate traffic flow. The length dependent transition has been observed for a range of maximum velocities greater than a certain value. Finite size scaling analysis indicates power-law scaling of these quantities at the onset of the jammed phase.
Empirical Features of Spontaneous and Induced Traffic Breakdowns in Free Flow at Highway Bottlenecks
Kerner, Boris S; Klenov, Sergey L; Rehborn, Hubert; Leibel, Michael
2015-01-01
Based on an empirical study of real field traffic data measured in 1996--2014 through road detectors installed on German freeways, we reveal physical features of empirical nuclei for spontaneous traffic breakdown in free flow at highway bottlenecks. It is shown that the source of a nucleus for traffic breakdown is the solely difference between empirical spontaneous and induced traffic breakdowns at a highway bottleneck. Microscopic traffic simulations with a stochastic traffic flow model in the framework of three-phase theory explain the empirical findings. It turns out that in the most cases, a nucleus for empirical spontaneous traffic breakdown occurs through an interaction of one of waves in free flow with an empirical permanent speed disturbance localized at a highway bottleneck. The wave is a localized structure in free flow, in which the total flow rate is larger and the speed averaged across the highway is smaller than outside the wave. The waves in free flow appear due to oscilations in the percentage...
A study of a main-road cellular automata traffic flow model
Institute of Scientific and Technical Information of China (English)
黄乒花; 孔令江; 刘慕仁
2002-01-01
A main-road cellular automata traffic flow model on two dimensions is presented based on the Biham-Middleton-Levine traffic model. Its evolution equations are given and the self-organization and organization cooperation phenomenain this model are also studied by using computer simulation.
Directory of Open Access Journals (Sweden)
Meng Chi
2014-01-01
Full Text Available In the large-scale distributed simulation area, the topology of the overlay network cannot always rapidly adapt to frequently changing application traffic to reduce the overall traffic cost. In this paper, we propose a self-adapting routing strategy for frequently changing application traffic in content-based publish/subscribe system. The strategy firstly trains the traffic information and then uses this training information to predict the application traffic in the future. Finally, the strategy reconfigures the topology of the overlay network based on this predicting information to reduce the overall traffic cost. A predicting path is also introduced in this paper to reduce the reconfiguration numbers in the process of the reconfigurations. Compared to other strategies, the experimental results show that the strategy proposed in this paper could reduce the overall traffic cost of the publish/subscribe system in less reconfigurations.
A Formalisation of Adaptable Pervasive Flows
Bucchiarone, Antonio; Lafuente, Alberto Lluch; Marconi, Annapaola; Pistore, Marco
Adaptable Pervasive Flows is a novel workflow-based paradigm for the design and execution of pervasive applications, where dynamic workflows situated in the real world are able to modify their execution in order to adapt to changes in their environment. In this paper, we study a formalisation of such flows by means of a formal flow language. More precisely, we define APFoL (Adaptable Pervasive Flow Language) and formalise its textual notation by encoding it in Blite, a formalisation of WS-BPEL. The encoding in Blite equips the language with a formal semantics and enables the use of automated verification techniques. We illustrate the approach with an example of a Warehouse Case Study.
A New Macro Model for Traffic Flow on a Highway with Ramps and Numerical Tests
Institute of Scientific and Technical Information of China (English)
TANG Tie-Qiao; HUANG Hai-Jun; S.C.Wong; GAO Zi-You; ZHANG Ying
2009-01-01
In this paper, we present a new macro model for traffic flow on a highway with ramps based on the existing models. We use the new model to study the effects of on-off-ramp on the main road traffic during the morning rush period and the evening rush period. Numerical tests show that, during the two rush periods, these effects are often different and related to the status of the main road traffic. If the main road traffic flow is uniform, then ramps always produce stop-and-go traffic when the main road density is between two critical values, and ramps have little effect on the main road traffic when the main road density is less than the smaller critical value or greater than the larger critical value. If a small perturbation appears on the main road, ramp may lead to stop-and-go traffic, or relieve or even eliminate the stop-and-go traffic, under different circumstances. These results are consistent with real traffic, which shows that the new model is reasonable.
Directory of Open Access Journals (Sweden)
Cheng Xu
2015-01-01
Full Text Available Free flow speed is a fundamental measure of traffic performance and has been found to affect the severity of crash risk. However, the previous studies lack analysis and modelling of impact factors on bicycles’ free flow speed. The main focus of this study is to develop multilayer back propagation artificial neural network (BPANN models for the prediction of free flow speed and crash risk on the separated bicycle path. Four different models with considering different combinations of input variables (e.g., path width, traffic condition, bicycle type, and cyclists’ characteristics were developed. 459 field data samples were collected from eleven bicycle paths in Hangzhou, China, and 70% of total samples were used for training, 15% for validation, and 15% for testing. The results show that considering the input variables of bicycle types and characteristics of cyclists will effectively improve the accuracy of the prediction models. Meanwhile, the parameters of bicycle types have more significant effect on predicting free flow speed of bicycle compared to those of cyclists’ characteristics. The findings could contribute for evaluation, planning, and management of bicycle safety.
Transition from Disorder to Order in Traffic Flow
Institute of Scientific and Technical Information of China (English)
LI Ke-Ping; GAO Zi-You
2004-01-01
We propose a new technique to investigate the dynamical transitions among the traffic phases. A type of the control signals has been designated at a given site (signal point) of the single-lane highway. Under the effect of the control signal, the velocity of the vehicle that passes the signal point will be changed periodically. Our method is tested for the deterministic NaSch traffic model. The simulation results demonstrate that the disorder states in the deterministic NaSch traffic model can be suppressed, and the different types of periodic states would occur.
Eulerian Air Traffic Flow Management Agent for the ACES Software Project
National Aeronautics and Space Administration — The development of an Eulerian model based en route traffic flow management agent for the ACES software is proposed. The proposed research will use a...
Traffic flow collection wireless sensor network node for intersection light control
Li, Xu; Li, Xue
2011-10-01
Wireless sensor network (WSN) is expected to be deployed in intersection to monitor the traffic flow continuously, and the monitoring datum can be used as the foundation of traffic light control. In this paper, a WSN based on ZigBee protocol for monitoring traffic flow is proposed. Structure, hardware and work flow of WSN nodes are designed. CC2431 from Texas Instrument is chosen as the main computational and transmission unit, and CC2591 as the amplification unit. The stability experiment and the actual environment experiment are carried out in the last of the paper. The results of experiments show that WSN has the ability to collect traffic flow information quickly and transmit the datum to the processing center in real time.
Applying the maximum information principle to cell transmission model of tra-ffic flow
Institute of Scientific and Technical Information of China (English)
刘喜敏; 卢守峰
2013-01-01
This paper integrates the maximum information principle with the Cell Transmission Model (CTM) to formulate the velo-city distribution evolution of vehicle traffic flow. The proposed discrete traffic kinetic model uses the cell transmission model to cal-culate the macroscopic variables of the vehicle transmission, and the maximum information principle to examine the velocity distri-bution in each cell. The velocity distribution based on maximum information principle is solved by the Lagrange multiplier method. The advantage of the proposed model is that it can simultaneously calculate the hydrodynamic variables and velocity distribution at the cell level. An example shows how the proposed model works. The proposed model is a hybrid traffic simulation model, which can be used to understand the self-organization phenomena in traffic flows and predict the traffic evolution.
Combination Adaptive Traffic Algorithm and Coordinated Sleeping in Wireless Sensor Network
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M. Udin Harun Al Rasyid
2014-12-01
Full Text Available Wireless sensor network (WSN uses a battery as its primary power source, so that WSN will be limited to battery power for long operations. The WSN should be able to save the energy consumption in order to operate in a long time.WSN has the potential to be the future of wireless communications solutions. WSN are small but has a variety of functions that can help human life. WSN has the wide variety of sensors and can communicate quickly making it easier for people to obtain information accurately and quickly. In this study, we combine adaptive traffic algorithms and coordinated sleeping as power‐efficient WSN solution. We compared the performance of our proposed ideas combination adaptive traffic and coordinated sleeping algorithm with non‐adaptive scheme. From the simulation results, our proposed idea has good‐quality data transmission and more efficient in energy consumption, but it has higher delay than that of non‐adaptive scheme. Keywords:WSN,adaptive traffic,coordinated sleeping,beacon order,superframe order.
Effect of the Primary User Traffic on Cognitive Relaying with Adaptive Transmission
Rao, Anlei
2012-09-08
In a cognitive-relay system, the secondary user is permitted to transmit data via a relay when the spectrum bands are detected to be free. The miss detection of spectrum sensing and the primary user traffic will affect the data transmission performance of the secondary user. In this paper, we investigate the impact of the status change of the primary user on the bit error rate (BER) of the adaptive transmission of the secondary user in a cognitive-relay system. Numerical results show that the primary user traffic can significantly degrade the BER of the secondary user transmission.
Jam Formation of Traffic Flow in Harbor Tunnel
Institute of Scientific and Technical Information of China (English)
何红弟; 卢伟真; 董力耘
2011-01-01
This paper reports a study concerning occurrence and growth of traffic jam in a harbor tunnel. The single-lane with three sections （downgrade, fiat, and upgrade） is taken into account and they are characterized with different velocity limit. At the low density, the traffic current increases linearly with density and saturates at some values of immediately density. As the density increases, the traffic jam appears firstly before the upgrade section and then extends to the downgrade section. Additionally, the relationships of the velocity and headway against position in different densities are obta/ned from simulation. These results clearly clarify where and when the traffic jam appears. Finally, the critical densities are derived via the theoretical analysis before and after the discontinuous fronts and the theoretical results are consistent with the critical values of simulation results.
Traffic flow in a Manhattan-like urban system
Li, Ming; Jiang, Rui; Hu, Mao-Bin; Wang, Bing-Hong
2011-01-01
In this paper, a cellular automaton model of vehicular traffic in Manhattan-like urban system is proposed. In this model, the origin-destination trips and traffic lights have been considered. The system exhibits three different states, i.e., moving state, saturation state and global deadlock state. With a grid coarsening method, vehicle distribution in the moving state and the saturation state has been studied. Interesting structures (e.g., windmill-like one, T-shirt-like one, Y-like one) have been revealed. A metastability of the system is observed in the transition from saturation state to global deadlock state. The effect of advanced traveller information system (ATIS), the traffic light period, and the traffic light switch strategy have also been investigated.
Staggered car-following induced by lateral separation effects in traffic flow
Jin, Sheng; Wang, Dian-hai; Xu, Cheng; Huang, Zhi-yi
2012-01-01
This Letter develops a new staggered car-following model taking into consideration lateral separation effects. Time-to-collision, calculated using visual angle variables, is introduced to describe the lateral separation distance and improve the optimal velocity model. The analytical and numerical results show that the stability of traffic flow can gradually be enhanced with the increase of lateral separation effects. The asymmetry property of traffic flow is also investigated using the new model. The results imply that incorporating lateral separation effects into the car-following model leads to the suppression of traffic jams and greatly enhances the realism of the model.
The effect of interruption probability in lattice model of two-lane traffic flow with passing
Peng, Guanghan
2016-11-01
A new lattice model is proposed by taking into account the interruption probability with passing for two-lane freeway. The effect of interruption probability with passing is investigated about the linear stability condition and the mKdV equation through linear stability analysis and nonlinear analysis, respectively. Furthermore, numerical simulation is carried out to study traffic phenomena resulted from the interruption probability with passing in two-lane system. The results show that the interruption probability with passing can improve the stability of traffic flow for low reaction coefficient while the interruption probability with passing can destroy the stability of traffic flow for high reaction coefficient on two-lane highway.
Directory of Open Access Journals (Sweden)
Hongying Jin
2013-10-01
Full Text Available This paper aims at effectively predicting the dynamic network traffic flow based on quantum-behaved particle swarm optimization algorithm. Firstly, the dynamic network traffic flow prediction problem is analyzed through formal description. Secondly, the structure of the network traffic flow prediction model is given. In this structure, Users can used a computer to start the traffic flow prediction process, and data collecting module can collect and return the data through the destination device. Thirdly, the dynamic network traffic flow prediction model is implemented based on BP Neural Network. Particularly, in this paper, the BP Neural Network is trained by a modified quantum-behaved particle swarm optimization(QPSO. We modified the QPSO by utilizing chaos signals to implement typical logistic mapping and pursuing the fitness function of a particle by a set of optimal parameters. Afterwards, based on the above process, dynamic network traffic flow prediction model is illustrated. Finally, a series of experiments are conduct to make performance evaluation, and related analyses for experimental results are also given
Kerner, Boris S
2015-12-01
We have revealed a growing local speed wave of increase in speed that can randomly occur in synchronized flow (S) at a highway bottleneck. The development of such a traffic flow instability leads to free flow (F) at the bottleneck; therefore, we call this instability an S→F instability. Whereas the S→F instability leads to a local increase in speed (growing acceleration wave), in contrast, the classical traffic flow instability introduced in the 1950s-1960s and incorporated later in a huge number of traffic flow models leads to a growing wave of a local decrease in speed (growing deceleration wave). We have found that the S→F instability can occur only if there is a finite time delay in driver overacceleration. The initial speed disturbance of increase in speed (called "speed peak") that initiates the S→F instability occurs usually at the downstream front of synchronized flow at the bottleneck. There can be many speed peaks with random amplitudes that occur randomly over time. It has been found that the S→F instability exhibits a nucleation nature: Only when a speed peak amplitude is large enough can the S→F instability occur; in contrast, speed peaks of smaller amplitudes cause dissolving speed waves of a local increase in speed (dissolving acceleration waves) in synchronized flow. We have found that the S→F instability governs traffic breakdown-a phase transition from free flow to synchronized flow (F→S transition) at the bottleneck: The nucleation nature of the S→F instability explains the metastability of free flow with respect to an F→S transition at the bottleneck.
Kerner, Boris S.
2015-12-01
We have revealed a growing local speed wave of increase in speed that can randomly occur in synchronized flow (S) at a highway bottleneck. The development of such a traffic flow instability leads to free flow (F) at the bottleneck; therefore, we call this instability an S →F instability. Whereas the S →F instability leads to a local increase in speed (growing acceleration wave), in contrast, the classical traffic flow instability introduced in the 1950s-1960s and incorporated later in a huge number of traffic flow models leads to a growing wave of a local decrease in speed (growing deceleration wave). We have found that the S →F instability can occur only if there is a finite time delay in driver overacceleration. The initial speed disturbance of increase in speed (called "speed peak") that initiates the S →F instability occurs usually at the downstream front of synchronized flow at the bottleneck. There can be many speed peaks with random amplitudes that occur randomly over time. It has been found that the S →F instability exhibits a nucleation nature: Only when a speed peak amplitude is large enough can the S →F instability occur; in contrast, speed peaks of smaller amplitudes cause dissolving speed waves of a local increase in speed (dissolving acceleration waves) in synchronized flow. We have found that the S →F instability governs traffic breakdown—a phase transition from free flow to synchronized flow (F →S transition) at the bottleneck: The nucleation nature of the S →F instability explains the metastability of free flow with respect to an F →S transition at the bottleneck.
Research on traffic flow forecasting model based on cusp catastrophe theory
Institute of Scientific and Technical Information of China (English)
张亚平; 裴玉龙
2004-01-01
This paper intends to describe the relationship between traffic parameters by using cusp catastrophe theory and to deduce highway capacity and corresponding speed forecasting value through suitable transformation of catastrophe model. The five properties of a catastrophe system are outlined briefly, and then the data collected on freeways of Zhujiang River Delta, Guangdong province, China are examined to ascertain whether they exhibit qualitative properties and attributes of the catastrophe model. The forecasting value of speed and capacity for freeway segments are given based on the catastrophe model. Furthermore, speed-flow curve on freeway is drawn by plotting out congested and uncongested traffic flow and the capacity value for the same freeway segment is also obtained from speed-flow curve to test the feasibility of the application of cusp catastrophe theory in traffic flow analysis. The calculating results of catastrophe model coincide with those of traditional traffic flow models regressed from field observed data, which indicates that the deficiency of traditional analysis of relationship between speed, flow and occupancy in two-dimension can be compensated by analysis of the relationship among speed, flow and occupancy based on catastrophe model in three-dimension. Finally, the prospects and problems of its application in traffic flow research in China are discussed.
Traffic Flow Condition Classification for Short Sections Using Single Microwave Sensor
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Memiş Kemal
2010-01-01
Full Text Available Daily observed traffic flow can show different characteristics varying with the times of the day. They are caused by traffic incidents such as accidents, disabled cars, construction activities and other unusual events. Three different major traffic conditions can be occurred: "Flow," "Dense" and "Congested". Objective of this research is to identify the current traffic condition by examining the traffic measurement parameters. The earlier researches have dealt only with speed and volume by ignoring occupancy. In our study, the occupancy is another important parameter of classification. The previous works have used multiple sensors to classify traffic condition whereas our work uses only single microwave sensor. We have extended Multiple Linear Regression classification with our new approach of Estimating with Error Prediction. We present novel algorithms of Multiclassification with One-Against-All Method and Multiclassification with Binary Comparison for multiple SVM architecture. Finaly, a non-linear model of backpropagation neural network is introduced for classification. This combination has not been reported on previous studies. Training data are obtained from the Corsim based microscopic traffic simulator TSIS 5.1. All performances are compared using this data set. Our methods are currently installed and running at traffic management center of 2.Ring Road in Istanbul.
Traffic Flow Condition Classification for Short Sections Using Single Microwave Sensor
Cinsdikici, Muhammed G.; Memiş, Kemal
2010-12-01
Daily observed traffic flow can show different characteristics varying with the times of the day. They are caused by traffic incidents such as accidents, disabled cars, construction activities and other unusual events. Three different major traffic conditions can be occurred: "Flow," "Dense" and "Congested". Objective of this research is to identify the current traffic condition by examining the traffic measurement parameters. The earlier researches have dealt only with speed and volume by ignoring occupancy. In our study, the occupancy is another important parameter of classification. The previous works have used multiple sensors to classify traffic condition whereas our work uses only single microwave sensor. We have extended Multiple Linear Regression classification with our new approach of Estimating with Error Prediction. We present novel algorithms of Multiclassification with One-Against-All Method and Multiclassification with Binary Comparison for multiple SVM architecture. Finaly, a non-linear model of backpropagation neural network is introduced for classification. This combination has not been reported on previous studies. Training data are obtained from the Corsim based microscopic traffic simulator TSIS 5.1. All performances are compared using this data set. Our methods are currently installed and running at traffic management center of 2.Ring Road in Istanbul.
The Traffic Adaptive Data Dissemination (TrAD) Protocol for both Urban and Highway Scenarios.
Tian, Bin; Hou, Kun Mean; Zhou, Haiying
2016-06-21
The worldwide economic cost of road crashes and injuries is estimated to be US$518 billion per year and the annual congestion cost in France is estimated to be €5.9 billion. Vehicular Ad hoc Networks (VANETs) are one solution to improve transport features such as traffic safety, traffic jam and infotainment on wheels, where a great number of event-driven messages need to be disseminated in a timely way in a region of interest. In comparison with traditional wireless networks, VANETs have to consider the highly dynamic network topology and lossy links due to node mobility. Inter-Vehicle Communication (IVC) protocols are the keystone of VANETs. According to our survey, most of the proposed IVC protocols focus on either highway or urban scenarios, but not on both. Furthermore, too few protocols, considering both scenarios, can achieve high performance. In this paper, an infrastructure-less Traffic Adaptive data Dissemination (TrAD) protocol which takes into account road traffic and network traffic status for both highway and urban scenarios will be presented. TrAD has double broadcast suppression techniques and is designed to adapt efficiently to the irregular road topology. The performance of the TrAD protocol was evaluated quantitatively by means of realistic simulations taking into account different real road maps, traffic routes and vehicular densities. The obtained simulation results show that TrAD is more efficient in terms of packet delivery ratio, number of transmissions and delay in comparison with the performance of three well-known reference protocols. Moreover, TrAD can also tolerate a reasonable degree of GPS drift and still achieve efficient data dissemination.
The Traffic Adaptive Data Dissemination (TrAD Protocol for both Urban and Highway Scenarios
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Bin Tian
2016-06-01
Full Text Available The worldwide economic cost of road crashes and injuries is estimated to be US$518 billion per year and the annual congestion cost in France is estimated to be €5.9 billion. Vehicular Ad hoc Networks (VANETs are one solution to improve transport features such as traffic safety, traffic jam and infotainment on wheels, where a great number of event-driven messages need to be disseminated in a timely way in a region of interest. In comparison with traditional wireless networks, VANETs have to consider the highly dynamic network topology and lossy links due to node mobility. Inter-Vehicle Communication (IVC protocols are the keystone of VANETs. According to our survey, most of the proposed IVC protocols focus on either highway or urban scenarios, but not on both. Furthermore, too few protocols, considering both scenarios, can achieve high performance. In this paper, an infrastructure-less Traffic Adaptive data Dissemination (TrAD protocol which takes into account road traffic and network traffic status for both highway and urban scenarios will be presented. TrAD has double broadcast suppression techniques and is designed to adapt efficiently to the irregular road topology. The performance of the TrAD protocol was evaluated quantitatively by means of realistic simulations taking into account different real road maps, traffic routes and vehicular densities. The obtained simulation results show that TrAD is more efficient in terms of packet delivery ratio, number of transmissions and delay in comparison with the performance of three well-known reference protocols. Moreover, TrAD can also tolerate a reasonable degree of GPS drift and still achieve efficient data dissemination.
An Open-Source Microscopic Traffic Simulator
Treiber, Martin; 10.1109/MITS.2010.939208
2010-01-01
We present the interactive Java-based open-source traffic simulator available at www.traffic-simulation.de. In contrast to most closed-source commercial simulators, the focus is on investigating fundamental issues of traffic dynamics rather than simulating specific road networks. This includes testing theories for the spatiotemporal evolution of traffic jams, comparing and testing different microscopic traffic models, modeling the effects of driving styles and traffic rules on the efficiency and stability of traffic flow, and investigating novel ITS technologies such as adaptive cruise control, inter-vehicle and vehicle-infrastructure communication.
Modeling of speed distribution for mixed bicycle traffic flow
Directory of Open Access Journals (Sweden)
Cheng Xu
2015-11-01
Full Text Available Speed is a fundamental measure of traffic performance for highway systems. There were lots of results for the speed characteristics of motorized vehicles. In this article, we studied the speed distribution for mixed bicycle traffic which was ignored in the past. Field speed data were collected from Hangzhou, China, under different survey sites, traffic conditions, and percentages of electric bicycle. The statistics results of field data show that the total mean speed of electric bicycles is 17.09 km/h, 3.63 km/h faster and 27.0% higher than that of regular bicycles. Normal, log-normal, gamma, and Weibull distribution models were used for testing speed data. The results of goodness-of-fit hypothesis tests imply that the log-normal and Weibull model can fit the field data very well. Then, the relationships between mean speed and electric bicycle proportions were proposed using linear regression models, and the mean speed for purely electric bicycles or regular bicycles can be obtained. The findings of this article will provide effective help for the safety and traffic management of mixed bicycle traffic.
Lattice models of traffic flow considering drivers' delay in response
Institute of Scientific and Technical Information of China (English)
Zhu Hui-Bing
2009-01-01
This paper proposes two lattice traffic models by taking into account the drivers'delay in response.The lattice versions of the hydrodynamic model are described by the differential-difference equation and difference-difference equation.respectively.The stability conditions for the two models are obtained by using the linear stability theory.The modified KdV equation near the critical point is derived to describe the traffic jam by using the reductive perturbation method,and the kink-antikink soliton solutions related to the traffic density waves are obtained.The results show that the drivers'delay in sensing headway plays an important role in jamming transition.
Kerner, Boris S
2015-01-01
We have revealed a growing local speed wave of increase in speed that can randomly occur in synchronized flow (S) at a highway bottleneck. The development of such a traffic flow instability leads to free flow (F) at the bottleneck; therefore, we call this instability as an S$\\rightarrow$F instability. Whereas the S$\\rightarrow$F instability leads to a local {\\it increase in speed} (growing acceleration wave), in contrast, the classical traffic flow instability introduced in 50s--60s and incorporated later in a huge number of traffic flow models leads to a growing wave of a local {\\it decrease in speed} (growing deceleration wave). We have found that the S$\\rightarrow$F instability can occur only, if there is a finite time delay in driver over-acceleration. The initial speed disturbance of increase in speed (called "speed peak") that initiates the S$\\rightarrow$F instability occurs usually at the downstream front of synchronized flow at the bottleneck. There can be many speed peaks with random amplitudes that ...
Cellular Automation Model of Traffic Flow Based on the Car-Following Model
Institute of Scientific and Technical Information of China (English)
LI Ke-Ping; GAO Zi-You
2004-01-01
@@ We propose a new cellular automation (CA) traffic model that is based on the car-following model. A class of driving strategies is used in the car-following model instead of the acceleration in the NaSch traffic model. In our model, some realistic driver behaviour and detailed vehicle characteristics have been taken into account, such as distance-headway and safe distance, etc. The simulation results show that our model can exhibit some traffic flow states that have been observed in the real traffic, and both of the maximum flux and the critical density are very close to the real measurement. Moreover, it is easy to extend our method to multi-lane traffic.
Stabilization and enhancement of traffic flow by the next-nearest-neighbor interaction.
Nagatani, T
1999-12-01
The car-following model of traffic is extended to take into account the car interaction before the next car ahead (the next-nearest-neighbor interaction). The traffic behavior of the extended car-following model is investigated numerically and analytically. It is shown that the next-nearest-neighbor interaction stabilizes the traffic flow. The jamming transition between the freely moving and jammed phases occurs at a higher density than the threshold of the original car-following model. By increasing the maximal velocity, the traffic current is enhanced without jam by the stabilization effect. The jamming transition is analyzed with the use of the linear stability and nonlinear perturbation methods. The traffic jam is described by the kink solution of the modified Korteweg-de Vries equation. The theoretical coexisting curve is in good agreement with the simulation result.
Canepa, Edward S.
2012-09-01
This article presents a new mixed integer programming formulation of the traffic density estimation problem in highways modeled by the Lighthill Whitham Richards equation. We first present an equivalent formulation of the problem using an Hamilton-Jacobi equation. Then, using a semi-analytic formula, we show that the model constraints resulting from the Hamilton-Jacobi equation result in linear constraints, albeit with unknown integers. We then pose the problem of estimating the density at the initial time given incomplete and inaccurate traffic data as a Mixed Integer Program. We then present a numerical implementation of the method using experimental flow and probe data obtained during Mobile Century experiment. © 2012 IEEE.
Jin, Cheng-Jie; Wang, Wei; Jiang, Rui; Zhang, H M; Wang, Hao
2013-01-01
Traffic flow complexity comes from the car-following and lane-changing behavior. Based on empirical data for individual vehicle speeds and time headways measured on a single-lane highway section, we have studied the traffic flow properties induced by pure car-following behavior. We have found that a spontaneous sudden drop in velocity could happen in a platoon of vehicles when the velocity of the leading vehicle is quite high (~70 km/h). In contrast, when the velocity of the leading vehicle in a platoon slows down, such a spontaneous sudden drop of velocity has not been observed. Our finding indicates that traffic breakdown on a single-lane road might be a phase transition from free flow to synchronized flow (F→S transition). We have found that the flow rate within the emergent synchronized flow can be either smaller or larger than the flow rate in the free flow within which the synchronized flow propagates. Our empirical findings support Kerner's three-phase theory in which traffic breakdown is associated with an F→S transition.
Price of anarchy on heterogeneous traffic-flow networks
Rose, A.; O'Dea, R.; Hopcraft, K. I.
2016-09-01
The efficiency of routing traffic through a network, comprising nodes connected by links whose cost of traversal is either fixed or varies in proportion to volume of usage, can be measured by the "price of anarchy." This is the ratio of the cost incurred by agents who act to minimize their individual expenditure to the optimal cost borne by the entire system. As the total traffic load and the network variability—parameterized by the proportion of variable-cost links in the network—changes, the behaviors that the system presents can be understood with the introduction of a network of simpler structure. This is constructed from classes of nonoverlapping paths connecting source to destination nodes that are characterized by the number of variable-cost edges they contain. It is shown that localized peaks in the price of anarchy occur at critical traffic volumes at which it becomes beneficial to exploit ostensibly more expensive paths as the network becomes more congested. Simulation results verifying these findings are presented for the variation of the price of anarchy with the network's size, aspect ratio, variability, and traffic load.
Anomaly Characterization in Flow-Based Traffic Time Series
Sperotto, A.; Sadre, R.; Pras, A.
2008-01-01
The increasing number of network attacks causes growing problems for network operators and users. Not only do these attacks pose direct security threats to our infrastructure, but they may also lead to service degradation, due to the massive traffic volume variations that are possible during such at
Bao, Xu; Li, Haijian; Xu, Dongwei; Jia, Limin; Ran, Bin; Rong, Jian
2016-11-06
The jam flow condition is one of the main traffic states in traffic flow theory and the most difficult state for sectional traffic information acquisition. Since traffic information acquisition is the basis for the application of an intelligent transportation system, research on traffic vehicle counting methods for the jam flow conditions has been worthwhile. A low-cost and energy-efficient type of multi-function wireless traffic magnetic sensor was designed and developed. Several advantages of the traffic magnetic sensor are that it is suitable for large-scale deployment and time-sustainable detection for traffic information acquisition. Based on the traffic magnetic sensor, a basic vehicle detection algorithm (DWVDA) with less computational complexity was introduced for vehicle counting in low traffic volume conditions. To improve the detection performance in jam flow conditions with a "tailgating effect" between front vehicles and rear vehicles, an improved vehicle detection algorithm (SA-DWVDA) was proposed and applied in field traffic environments. By deploying traffic magnetic sensor nodes in field traffic scenarios, two field experiments were conducted to test and verify the DWVDA and the SA-DWVDA algorithms. The experimental results have shown that both DWVDA and the SA-DWVDA algorithms yield a satisfactory performance in low traffic volume conditions (scenario I) and both of their mean absolute percent errors are less than 1% in this scenario. However, for jam flow conditions with heavy traffic volumes (scenario II), the SA-DWVDA was proven to achieve better results, and the mean absolute percent error of the SA-DWVDA is 2.54% with corresponding results of the DWVDA 7.07%. The results conclude that the proposed SA-DWVDA can implement efficient and accurate vehicle detection in jam flow conditions and can be employed in field traffic environments.
Directory of Open Access Journals (Sweden)
Xu Bao
2016-11-01
Full Text Available The jam flow condition is one of the main traffic states in traffic flow theory and the most difficult state for sectional traffic information acquisition. Since traffic information acquisition is the basis for the application of an intelligent transportation system, research on traffic vehicle counting methods for the jam flow conditions has been worthwhile. A low-cost and energy-efficient type of multi-function wireless traffic magnetic sensor was designed and developed. Several advantages of the traffic magnetic sensor are that it is suitable for large-scale deployment and time-sustainable detection for traffic information acquisition. Based on the traffic magnetic sensor, a basic vehicle detection algorithm (DWVDA with less computational complexity was introduced for vehicle counting in low traffic volume conditions. To improve the detection performance in jam flow conditions with a “tailgating effect” between front vehicles and rear vehicles, an improved vehicle detection algorithm (SA-DWVDA was proposed and applied in field traffic environments. By deploying traffic magnetic sensor nodes in field traffic scenarios, two field experiments were conducted to test and verify the DWVDA and the SA-DWVDA algorithms. The experimental results have shown that both DWVDA and the SA-DWVDA algorithms yield a satisfactory performance in low traffic volume conditions (scenario I and both of their mean absolute percent errors are less than 1% in this scenario. However, for jam flow conditions with heavy traffic volumes (scenario II, the SA-DWVDA was proven to achieve better results, and the mean absolute percent error of the SA-DWVDA is 2.54% with corresponding results of the DWVDA 7.07%. The results conclude that the proposed SA-DWVDA can implement efficient and accurate vehicle detection in jam flow conditions and can be employed in field traffic environments.
A Study on the Model of Traffic Flow and Vehicle Exhaust Emission
Directory of Open Access Journals (Sweden)
Han Xue
2013-01-01
Full Text Available The increase of traffic flow in cities causes traffic congestion and accidents as well as air pollution. Traffic problems have attracted the interest of many researchers from the perspective of theory and engineering. In order to provide a simple and practical method for measuring the exhaust emission and assessing the effect of pollution control, a model is based on the relationship between traffic flow and vehicle exhaust emission under a certain level of road capacity constraints. In the proposed model, the hydrocarbons (HC, carbon monoxide (CO, and nitrogen oxides (NOx are considered as the indexes of total exhaust emission, and the speed is used as an intermediate variable. To verify the rationality and practicality of the model, a case study for Beijing, China, is provided in which the effects of taxi fare regulation and the specific vehicle emission reduction policy are analyzed.
Providing QoS guarantees for self-similar traffic flows
Institute of Scientific and Technical Information of China (English)
Wen Jun; Zhang Rui; Lu Xianliang
2005-01-01
Provisioning network resource to meet the quality of Service (QoS) demand isa key issue for future network services. Such functions may be realized by an admission control algorithm, which determines whether or not a new traffic flow can be admitted into the network. It is widely accepted that many traffic flows have self-similar character that has detrimental influence on network performance. This characteristic has made old mathematical models invalid, and a new model must work with self-similar fractal instead. This paper applies Fractional Brownian Motion(FBM) model and integrates it into the comprehensive admission control scheme, which takes account of aggregated traffic behavior to get the statistical multiplexing performance gain. Experiment verifies that FBM model can be used to realistically describe packet traffic in modern packet networks and accurately predict their performance.
Intra-City Urban Network and Traffic Flow Analysis from GPS Mobility Trace
Leung, Ian X Y; Hui, Pan; Lio', Pietro
2011-01-01
We analyse two large-scale intra-city urban networks and traffic flows therein measured by GPS traces of taxis in San Francisco and Shanghai. Our results coincide with previous findings that, based purely on topological means, it is often insufficient to characterise traffic flow. Traditional shortest-path betweenness analysis, where shortest paths are calculated from each pairs of nodes, carries an unrealistic implicit assumption that each node or junction in the urban network generates and attracts an equal amount of traffic. We also argue that weighting edges based only on euclidean distance is inadequate, as primary roads are commonly favoured over secondary roads due to the perceived and actual travel time required. We show that betweenness traffic analysis can be improved by a simple extended framework which incorporates both the notions of node weights and fastest-path betweenness. We demonstrate that the framework is superior to traditional methods based solely on simple topological perspectives.
Optimization model and algorithm for mixed traffic of urban road network with flow interference
Institute of Scientific and Technical Information of China (English)
SI BingFeng; LONG JianCeng; GAO ZiYou
2008-01-01
In this paper, the problem of interferences between motors and non-motors in ur-ban road mixed traffic network is considered and the corresponding link imped-ance function is presented based on travel demand, On the base of this, the main factors that influence travelers' traffic choices are all considered and a combined model including flow-split and assignment problem is proposed, Then a bi-level model with its algorithm for system optimization of urban road mixed traffic net-work is proposed. Finally the application of the model and its algorithm is illus-trated with a numerical example.
Effect of looking backward on traffic flow in a cooperative driving car following model
Ge, H. X.; Zhu, H. B.; Dai, S. Q.
2006-12-01
An extended car following model is proposed by incorporating intelligent transportation system and the backward looking effect under certain condition in traffic flow. The neutral stability condition of this model is obtained by using the linear stability theory. The results show that anticipating the behavior of vehicles preceding and following one vehicle could lead to appreciable stabilization of traffic system. From the simulation of space-time evolution of the vehicle headways, it is shown that the traffic jam could be suppressed efficiently via taking into account the information about the motion of two preceding vehicles and one following vehicle, and the analytical result is consistent with the simulation one.
A new lattice hydrodynamic traffic flow model with a consideration of multi-anticipation effect
Institute of Scientific and Technical Information of China (English)
Tian Chuan; Sun Di-Hua; Yang Shu-Hong
2011-01-01
We present a new multi-anticipation lattice hydrodynamic model based on the traffic anticipation effect in the real world.Applying the linear stability theory,we obtain the linear stability condition of the model.Through nonlinear analysis,we derive the modified Korteweg-de Vries equation to describe the propagating behaviour of a traffic density wave near the critical point.The good agreement between the simulation results and the analytical results shows that the stability of traffic flow can be enhanced when the multi-anticipation effect is considered.
Optimization model and algorithm for mixed traffic of urban road network with flow interference
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper,the problem of interferences between motors and non-motors in urban road mixed traffic network is considered and the corresponding link impedance function is presented based on travel demand.On the base of this,the main factors that influence travelers’ traffic choices are all considered and a combined model including flow-split and assignment problem is proposed.Then a bilevel model with its algorithm for system optimization of urban road mixed traffic network is proposed.Finally the application of the model and its algorithm is illus-trated with a numerical example.
Density waves in a lattice hydrodynamic traffic flow model with the anticipation effect
Institute of Scientific and Technical Information of China (English)
Zhao Min; Sun Di-Hua; Tian Chuan
2012-01-01
By introducing the traffic anticipation effect in the real world into the original lattice hydrodynamic model,we present a new anticipation effect lattice hydrodynamic (AELH) model,and obtain the linear stability condition of the model by applying the linear stability theory.Through nonlinear analysis,we derive the Burgers equation and Korteweg-de Vries (KdV) equation,to describe the propagating behaviour of traffic density waves in the stable and the metastable regions,respectively.The good agreement between simulation results and analytical results shows that the stability of traffic flow can be enhanced when the anticipation effect is considered.
The impact of traffic-flow patterns on air quality in urban street canyons.
Thaker, Prashant; Gokhale, Sharad
2016-01-01
We investigated the effect of different urban traffic-flow patterns on pollutant dispersion in different winds in a real asymmetric street canyon. Free-flow traffic causes more turbulence in the canyon facilitating more dispersion and a reduction in pedestrian level concentration. The comparison of with and without a vehicle-induced-turbulence revealed that when winds were perpendicular, the free-flow traffic reduced the concentration by 73% on the windward side with a minor increase of 17% on the leeward side, whereas for parallel winds, it reduced the concentration by 51% and 29%. The congested-flow traffic increased the concentrations on the leeward side by 47% when winds were perpendicular posing a higher risk to health, whereas reduced it by 17-42% for parallel winds. The urban air quality and public health can, therefore, be improved by improving the traffic-flow patterns in street canyons as vehicle-induced turbulence has been shown to contribute significantly to dispersion.
HFBP: Identifying P2P Traffic by Host Level and Flow Level Behavior Profiles
Directory of Open Access Journals (Sweden)
Jinghua Yan
2013-08-01
Full Text Available Recently, Peer-to-peer (P2P networks have been widely applied in streaming media, instant messaging, file sharing and other fields, which have occupied more and more network bandwidth. Accurately identify P2P traffic is very important to management and control P2P traffic. In this paper, we introduce HFBP, a novel P2P identification scheme based on the host level and flow level behavior profiles of P2P traffic. HFBP consists of two stages. In the first stage, we calculate the probability that a host takes part in P2P application by matching its behavior with some host level behavior rules. In the second stage, we compute the probability that a flow belonging to P2P application by comparing the statistical features of each flow in the host with several flow feature profiles. We evaluate HFBP using real traffic traces. The identification accuracy achieves 93.1% and 95.1% in terms of flow and byte respectively. The experimental results prove that HFBP obtains satisfactory performance in identifying P2P traffic.
Optimized Structure of the Traffic Flow Forecasting Model With a Deep Learning Approach.
Yang, Hao-Fan; Dillon, Tharam S; Chen, Yi-Ping Phoebe
2016-07-20
Forecasting accuracy is an important issue for successful intelligent traffic management, especially in the domain of traffic efficiency and congestion reduction. The dawning of the big data era brings opportunities to greatly improve prediction accuracy. In this paper, we propose a novel model, stacked autoencoder Levenberg-Marquardt model, which is a type of deep architecture of neural network approach aiming to improve forecasting accuracy. The proposed model is designed using the Taguchi method to develop an optimized structure and to learn traffic flow features through layer-by-layer feature granulation with a greedy layerwise unsupervised learning algorithm. It is applied to real-world data collected from the M6 freeway in the U.K. and is compared with three existing traffic predictors. To the best of our knowledge, this is the first time that an optimized structure of the traffic flow forecasting model with a deep learning approach is presented. The evaluation results demonstrate that the proposed model with an optimized structure has superior performance in traffic flow forecasting.
Redhu, Poonam; Gupta, Arvind Kumar
2015-03-01
A new lattice hydrodynamic model is proposed by considering the interruption probability effect on traffic flow with passing and analyzed both theoretically and numerically. From linear and non-linear stability analysis, the effect of interruption probability on the phase diagram is investigated and the condition of existence for kink-antikink soliton solution of mKdV equation is derived. The stable region is enhanced with interruption probability and the jamming transition occurs from uniform flow to kink flow through chaotic flow for higher and intermediate values of non-interruption effect of passing. It is also observed that there exists conventional jamming transition between uniform flow and kink flow for lower values of non-interruption effect of passing. Numerical simulations are carried out and found in accordance with the theoretical findings which confirm that the effect of interruption probability plays an important role in stabilizing traffic flow when passing is allowed.
Cluster-size dependent randomization traffic flow model
Institute of Scientific and Technical Information of China (English)
Gao Kun; Wang Bing-Hong; Fu Chuan-Ji; Lu Yu-Feng
2007-01-01
In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic,the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters'size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speeddependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.
Analysis of kinematic waves arising in diverging traffic flow models
Jin, Wen-Long
2010-01-01
Diverging junctions are important network bottlenecks, and a better understanding of diverging traffic dynamics has both theoretical and practical implications. In this paper, we first introduce a continuous multi-commodity kinematic wave model of diverging traffic and then present a new framework for constructing kinematic wave solutions to its Riemann problem with jump initial conditions. In supply-demand space, the solutions on a link consist of an interior state and a stationary state, subject to admissible conditions such that there are no positive and negative kinematic waves on the upstream and downstream links respectively. In addition, the solutions have to satisfy entropy conditions consistent with various discrete diverge models. In the proposed analytical framework, kinematic waves on each link can be uniquely determined by the stationary and initial conditions, and we prove that the stationary states and boundary fluxes exist and are unique for the Riemann problem of diverge models when all or pa...
Car Delay Model near Bus Stops with Mixed Traffic Flow
Directory of Open Access Journals (Sweden)
Yang Xiaobao
2013-01-01
Full Text Available This paper proposes a model for estimating car delays at bus stops under mixed traffic using probability theory and queuing theory. The roadway is divided to serve motorized and nonmotorized traffic streams. Bus stops are located on the nonmotorized lanes. When buses dwell at the stop, they block the bicycles. Thus, two conflict points between car stream and other traffic stream are identified. The first conflict point occurs as bicycles merge to the motorized lane to avoid waiting behind the stopping buses. The second occurs as buses merge back to the motorized lane. The average car delay is estimated as the sum of the average delay at these two conflict points and the delay resulting from following the slower bicycles that merged into the motorized lane. Data are collected to calibrate and validate the developed model from one site in Beijing. The sensitivity of car delay to various operation conditions is examined. The results show that both bus stream and bicycle stream have significant effects on car delay. At bus volumes above 200 vehicles per hour, the curbside stop design is not appropriate because of the long car delays. It can be replaced by the bus bay design.
Kerner, Boris S
2016-01-01
We show that the minimization of travel times in a network as generally accepted in classical traffic and transportation theories deteriorates the traffic system through a considerable increase in the probability of traffic breakdown in the network. We introduce a network characteristic {\\it minimum network capacity} that shows that rather than the minimization of travel times in the network, the minimization of the probability of traffic breakdown in the network maximizes the network throughput at which free flow persists in the whole network.
Traffic Flow Prediction Model for Large-Scale Road Network Based on Cloud Computing
Directory of Open Access Journals (Sweden)
Zhaosheng Yang
2014-01-01
Full Text Available To increase the efficiency and precision of large-scale road network traffic flow prediction, a genetic algorithm-support vector machine (GA-SVM model based on cloud computing is proposed in this paper, which is based on the analysis of the characteristics and defects of genetic algorithm and support vector machine. In cloud computing environment, firstly, SVM parameters are optimized by the parallel genetic algorithm, and then this optimized parallel SVM model is used to predict traffic flow. On the basis of the traffic flow data of Haizhu District in Guangzhou City, the proposed model was verified and compared with the serial GA-SVM model and parallel GA-SVM model based on MPI (message passing interface. The results demonstrate that the parallel GA-SVM model based on cloud computing has higher prediction accuracy, shorter running time, and higher speedup.
Anticipation Driving Behavior and Related Reduction of Energy Consumption in Traffic Flow
Shi, Wei; Wei, Yan-Fang; Song, Tao; Dai, Shi-Qiang; Dong, Li-Yun
In view that drivers would pay attention to the variation of headway on roads, an extended optimal velocity model is proposed by considering anticipation driving behavior. A stability criterion is given through linear stability analysis of traffic flows. The mKdV equation is derived with the reductive perturbation method for headway evolution which could be used to describe the stop-and-go traffic phenomenon. The results show a good effect of anticipation driving behavior on the stabilization of car flows and the anticipation driving behavior can improve the numerical stability of the model as well. In addition, the fluctuation of kinetic energy and the consumption of average energy in congested traffic flows are systematically analyzed. The results show that the reasonable level of anticipation driving behavior can save energy consumption in deceleration process effectively and lead to an associated relation like a "bow-tie" between the energy-saving and the value of anticipation factor.
Three phase classification of an uninterrupted traffic flow: a $k$-means clustering study
Kouhi, Reihaneh; Akbarzadeh, Meisam
2016-01-01
We investigate the speed time series of the vehicles recorded by a camera at a section of a highway in the city of Isfahan, Iran. Using $k$-means clustering algorithm, we find that the natural number of clustering for this set of data is $3$. This is in agreement with the three-phase theory of uninterrupted traffic flows. According to this theory, the three traffic phases are categorized as {\\em free flow} (F), {\\em synchronized} (S) and {\\em wide moving jam} (J). We obtain the transition speeds and densities at F-S and also S-J transitions. We also apply the Shannon entropy analysis on the speed time series over finite windows, which equips us to monitor in areal time the instant state of a traffic flow.
On the effect of stochastic transition in the fundamental diagram of traffic flow
Siqueira, Adriano Francisco; Wu, Chen; Qian, Wei-Liang
2014-01-01
In this work, we propose an alternative stochastic model for the fundamental diagram of traffic flow with minimal number of parameters. Our approach is based on a mesoscopic viewpoint of the traffic system in terms of the dynamics of vehicle velocity transitions. A key feature of the present approach lies in its stochastic nature which makes it possible to describe not only the flow-concentration relation, the so-called fundamental diagram in traffic engineering, but also its variance -- an important ingredient in the observed data of traffic flow. It is shown that the model can be seen as a derivative of the Boltzmann equation when assuming a discrete velocity spectrum. The latter assumption significantly simplifies the mathematics and therefore, facilitates the study of its physical content through the analytic solutions. The model parameters are then adjusted to reproduce the observed traffic flow on the "23 de maio" highway in the Brazilian city of Sao Paulo, where both the fundamental diagram and its var...
Doulamis, A D; Doulamis, N D; Kollias, S D
2003-01-01
Multimedia services and especially digital video is expected to be the major traffic component transmitted over communication networks [such as internet protocol (IP)-based networks]. For this reason, traffic characterization and modeling of such services are required for an efficient network operation. The generated models can be used as traffic rate predictors, during the network operation phase (online traffic modeling), or as video generators for estimating the network resources, during the network design phase (offline traffic modeling). In this paper, an adaptable neural-network architecture is proposed covering both cases. The scheme is based on an efficient recursive weight estimation algorithm, which adapts the network response to current conditions. In particular, the algorithm updates the network weights so that 1) the network output, after the adaptation, is approximately equal to current bit rates (current traffic statistics) and 2) a minimal degradation over the obtained network knowledge is provided. It can be shown that the proposed adaptable neural-network architecture simulates a recursive nonlinear autoregressive model (RNAR) similar to the notation used in the linear case. The algorithm presents low computational complexity and high efficiency in tracking traffic rates in contrast to conventional retraining schemes. Furthermore, for the problem of offline traffic modeling, a novel correlation mechanism is proposed for capturing the burstness of the actual MPEG video traffic. The performance of the model is evaluated using several real-life MPEG coded video sources of long duration and compared with other linear/nonlinear techniques used for both cases. The results indicate that the proposed adaptable neural-network architecture presents better performance than other examined techniques.
3D Markov Process for Traffic Flow Prediction in Real-Time
Directory of Open Access Journals (Sweden)
Eunjeong Ko
2016-01-01
Full Text Available Recently, the correct estimation of traffic flow has begun to be considered an essential component in intelligent transportation systems. In this paper, a new statistical method to predict traffic flows using time series analyses and geometric correlations is proposed. The novelty of the proposed method is two-fold: (1 a 3D heat map is designed to describe the traffic conditions between roads, which can effectively represent the correlations between spatially- and temporally-adjacent traffic states; and (2 the relationship between the adjacent roads on the spatiotemporal domain is represented by cliques in MRF and the clique parameters are obtained by example-based learning. In order to assess the validity of the proposed method, it is tested using data from expressway traffic that are provided by the Korean Expressway Corporation, and the performance of the proposed method is compared with existing approaches. The results demonstrate that the proposed method can predict traffic conditions with an accuracy of 85%, and this accuracy can be improved further.
Institute of Scientific and Technical Information of China (English)
梅超群; 刘业进
2011-01-01
In this paper, we develop a cellular automaton model to describe the phase transition of traffic flow on urban expressway systems with on-off-ramps and accessory roads. The lane changing rules are given in detailed, the numerical results show that the main road and the accessory road both produce phase transitions. These phase transitions will omen be influenced by the number of lanes, lane changing, the ramp flow, the input flow rate, and the geometry structure.
Kerner, Boris S.; Koller, Micha; Klenov, Sergey L.; Rehborn, Hubert; Leibel, Michael
2015-11-01
Based on an empirical study of real field traffic data measured in 1996-2014 through road detectors installed on German freeways, we reveal physical features of empirical nuclei for spontaneous traffic breakdown in free flow at highway bottlenecks. A microscopic stochastic three-phase traffic model of the nucleation of spontaneous traffic breakdown presented in the article explains the empirical findings. It turns out that in the most cases a nucleus for the breakdown occurs through an interaction of one of waves in free flow with an empirical permanent speed disturbance localized at a highway bottleneck. The wave is a localized structure in free flow, in which the total flow rate is larger and the speed averaged across the highway is smaller than outside the wave. The waves in free flow appear due to oscillations in the percentage of slow vehicles; these waves propagate with the average speed of slow vehicles in free flow. Any of the empirical waves exhibits a two-dimensional asymmetric spatiotemporal structure: Wave's characteristics are different in different highway lanes.
Kinetic description of bottleneck effects in traffic flow
Institute of Scientific and Technical Information of China (English)
Peng ZHANG; Dong-yan WU; S. C. WONG; Yi-zhou TAO
2009-01-01
This paper deals with the effects of traffic bottlenecks using an extended Lighthill-Whitham-Richards (LWR) model. The solution structure is analytically indi-cated by the study of the Riemann problem characterized by a discontinuous flux. This leads to a typical solution describing a queue upstream of the bottleneck and its width and height, and informs the design of a 5-mapping algorithm. More significantly, it is found that the kinetic model is able to reproduce stop-and-go waves for a triangular fun-damental diagram. Some simulation examples, which are in agreement with the analytical solutions, are given to support these conclusions.
Effect of optimal estimation of flux difference information on the lattice traffic flow model
Yang, Shu-hong; Li, Chun-gui; Tang, Xin-lai; Tian, Chuan
2016-12-01
In this paper, a new lattice model is proposed by considering the optimal estimation of flux difference information. The effect of this new consideration upon the stability of traffic flow is examined through linear stability analysis. Furthermore, a modified Korteweg-de Vries (mKdV) equation near the critical point is constructed and solved by means of nonlinear analysis method, and thus the propagation behavior of traffic jam can be described by the kink-antikink soliton solution of the mKdV equation. Numerical simulation is carried out under periodical condition with results in good agreement with theoretical analysis, therefore, it is verified that the new consideration can enhance the stability of traffic systems and suppress the emergence of traffic jams effectively.
A mesoscopic approach on stability and phase transition between different traffic flow states
Qian, Wei-Liang; Lin, Kai; Machado, Romuel F; Hama, Yogiro
2015-01-01
It is understood that congestion in traffic can be interpreted in terms of the instability of the equation of dynamic motion. The evoltuion of a traffic system from an unstable or metastable state to a globally stable state bears a strong resemblance to the phase transition in thermodynamics. In this work, we explore the underlying physics of the traffic system, by examing closely the physical properties and mathematical constraints of the phase transitons therein. By using a mesoscopic approach, one entitles the catastrophe model the same physical content as in the Landau's theory, and uncovers its close connection to the instability and phase transitions. In addition to the one-dimensional configuration space, we generalize our discussion to the higher-dimensional case, where the observed temporal oscillation in traffic flow data is attributed to the curl of a vector field. We exhibit that our model can reproduce main features of the observed fundamental diagram including the inverse-$\\lambda$ shape and the...
Delay Estimates of Mixed Traffic Flow at Signalized Intersections in China
Institute of Scientific and Technical Information of China (English)
SU Yuelong; WEI Zheng; CHENG Sihan; YAO Danya; ZHANG Yi; LI Li
2009-01-01
Two characteristics of Chinese mixed traffic invalidate the conventional queuing delay estimates for western countries. First, the driving characteristics of Chinese drivers lead to different delays even though the other conditions are the same. Second, urban traffic flow in China is often hindered by pedestrians at intersections, such that imported intelligent traffic control systems do not work appropriately. Typical delay estimates for Chinese conditions were obtained from data for over 500 vehicle queues in Beijing collected using charge coupled device (CCD) cameras. The results show that the delays mainly depend on the pro-portion and positions of heavy vehicles in the queue, as well as the start-up situations (with or without inter-ference). A simplified delay estimation model considers vehicle types and positions that compares well with the observed traffic delays.
Fuzzy State Transition and Kalman Filter Applied in Short-Term Traffic Flow Forecasting.
Deng, Ming-jun; Qu, Shi-ru
2015-01-01
Traffic flow is widely recognized as an important parameter for road traffic state forecasting. Fuzzy state transform and Kalman filter (KF) have been applied in this field separately. But the studies show that the former method has good performance on the trend forecasting of traffic state variation but always involves several numerical errors. The latter model is good at numerical forecasting but is deficient in the expression of time hysteretically. This paper proposed an approach that combining fuzzy state transform and KF forecasting model. In considering the advantage of the two models, a weight combination model is proposed. The minimum of the sum forecasting error squared is regarded as a goal in optimizing the combined weight dynamically. Real detection data are used to test the efficiency. Results indicate that the method has a good performance in terms of short-term traffic forecasting.
Dynamic simulation of energy consumption in mixed traffic flow considering highway toll station
Qian, Yong-Sheng; Zhang, Xiao-Long; Zeng, Jun-Wei; Shao, Xiao-Ming; Wang, Neng
2015-01-01
An improved model of energy consumption including toll station is presented in this paper. Using the model, we study the influences of mixed ratio, the idling energy consumption of vehicle, vehicle peak velocity, dwell time and random deceleration probability on energy consumption of Electronic Toll Collection or Manual Toll Collection mixed traffic flow on single lane under periodic condition. Simulating results indicate that the above five parameters are all increasing functions of total energy consumption, in which the idling energy consumption represents the major amounts with the increase of mixed ratio and occupancy rate. Thus, the existence of toll station has significant effect on the energy consumption of mixed traffic flow.
Wave propagation of the traffic flow dynamic model based on wavefront expansion
Institute of Scientific and Technical Information of China (English)
李莉; 施鹏飞
2004-01-01
This paper discusses propagation of perturbations along traffic flow modeled by a modified second-order macroscopic model through the wavefront expansion technique. The coefficients in this expansion satisfy a sequence of transport equations that can be solved analytically. One of these analytic solutions yields information about wavefront shock. Numerical simulations based on a Padé approximation of this expansion were done at the end of this paper and results showed that propagation of perturbations at traffic flow speed conforms to the theoretical analysis results.
The CA model for traffic-flow at the grade roundabout crossing
Institute of Scientific and Technical Information of China (English)
Chen Rui-Xiong; Bai Ke-Zhao; Liu Mu-Ren
2006-01-01
The cellular automaton model is suggested to describe the traffic-flow at the grade roundabout crossing. After the simulation with computer, the fundamental properties of this model have been revealed. Analysing this kind of road structure, this paper transforms the grade roundabout crossing with inner-roundabout-lane and outer-roundabout-lane into a configuration with many bottlenecks. Because of the self-organization, the traffic flow remains unblocked under a certain vehicle density. Some results of the simulation are close to the actual design parameter.
Dynamical evolution processes of traffic flow and travel cost in urban transportation networks
Institute of Scientific and Technical Information of China (English)
Guo Ren-Yong; Huang Hai-Jun
2008-01-01
Considering such a fact that travellers dynamically adjust their routes and the resultant link traffic flows in a network evolve over time,this paper proposes a dynamical evolutionary model of the traffic assignment problem with endogenous origin-destination (OD) demands.The model's stability is analysed and the resultant user equilibrium (UE) state is shown to be stable under certain conditions.Numerical results in a grid network indicate that the model can generate convergent flow patterns and finally terminates at the UE state.Impacts by the parameters associated with OD demand function and link cost function are also investigated.
Derivation, calibration and verification of macroscopic model for urban traffic flow. Part 2
Alekseenko, Andrey E; Kholodov, Aleksandr S; Goreva, Anna I; Kurzhanskiy, Alexander A; Chehovich, Yuriy V; Starozhilets, Vsevolod M
2016-01-01
In this paper, we propose a unified procedure for calibration of macroscopic second-order multilane traffic models. The focus is on calibrating the fundamental diagram using the combination stationary detector data and GPS traces. GPS traces are used in estimation of the deceleration wave speed. Thus calibrated model adequately represents the three phases of traffic: free flow, synchronized flow and the wide moving jam. The proposed approach was validated in simulation using stationary detection data and GPS traces from the Moscow Ring Road. Simulation showed that the proposed second-order model is more accurate than the first-order LWR model.
Solitary Density Waves for Improved Traffic Flow Model with Variable Brake Distances
Institute of Scientific and Technical Information of China (English)
朱文兴; 丁瑞玲
2012-01-01
Traffic flow model is improved by introducing variable brake distances with varying slopes. Stability of the traffic flow on a gradient is analyzed and the neutral stability condition is obtained. The KdV （Korteweg-de Vries） equation is derived the use of nonlinear analysis and soliton solution is obtained in the meta-stable region. Solitary density waves are reproduced in the numerical simulations. It is found that as uniform headway is less than the safety distance solitary wave exhibits upward form, otherwise it exhibits downward form. In general the numerical results are in good agreement with the analytical results.
The Investigation of the Traffic Flow Behavior in Tollbooths Using Cellular Automaton Model
Jetto, K.; Ez-Zahraouy, H.; Benyoussef, A.
Tollbooths are used to collect tolls and to control traffic flow. However, the presence of these tollbooths will slow down traffic, especially in heavily traveled roads. As a consequence, drivers and goods will spend more time and fuel waiting in a long queue. Unfortunately, there are a few papers in the literature, which have been addressed the effect of tollbooths on the traffic flow; whereas in this paper is, the properties of traffic flow inside the tollbooths are investigated. The proposed cellular automaton traffic model, with open boundaries, is based on some changing lane rules, which are inspired on the situations inside the toll plaza. The vehicles enter the plaza with an injecting rate α, and they leave with an extracting rate β, which is inversely proportional to the time service Tw. The simulation results show the existence of three phases in the phase diagram (α, β), namely: the low density phase, the congested phase, and the jamming phase. Furthermore, it is found that the vehicles does not spend the same time Tm in the plaza, even if they have the same time service. This analysis states clearly that the existence of the congested phase and the fluctuation Tm are due to the non-zero values of the probability P of changing the lane. Such phenomena disappear when P = 0, i.e., the drivers move without changing their lane. In other words, the human behavior (spontaneous changing lanes) is responsible for the congestion observed in the tollbooth.
SMART VIDEO SURVEILLANCE SYSTEM FOR VEHICLE DETECTION AND TRAFFIC FLOW CONTROL
Directory of Open Access Journals (Sweden)
A. A. SHAFIE
2011-08-01
Full Text Available Traffic signal light can be optimized using vehicle flow statistics obtained by Smart Video Surveillance Software (SVSS. This research focuses on efficient traffic control system by detecting and counting the vehicle numbers at various times and locations. At present, one of the biggest problems in the main city in any country is the traffic jam during office hour and office break hour. Sometimes it can be seen that the traffic signal green light is still ON even though there is no vehicle coming. Similarly, it is also observed that long queues of vehicles are waiting even though the road is empty due to traffic signal light selection without proper investigation on vehicle flow. This can be handled by adjusting the vehicle passing time implementing by our developed SVSS. A number of experiment results of vehicle flows are discussed in this research graphically in order to test the feasibility of the developed system. Finally, adoptive background model is proposed in SVSS in order to successfully detect target objects such as motor bike, car, bus, etc.
Tang, Tie-Qiao; Huang, Hai-Jun; Shang, Hua-Yan
2017-02-01
In this paper, we propose a macro traffic flow model to explore the effects of the driver's bounded rationality on the evolutions of traffic waves (which include shock and rarefaction waves) and small perturbation, and on the fuel consumption and emissions (that include CO, HC and NOX) during the evolution process. The numerical results illustrate that considering the driver's bounded rationality can prominently smooth the wavefront of the traffic waves and improve the stability of traffic flow, which shows that the driver's bounded rationality has positive impacts on traffic flow; but considering the driver's bounded rationality reduces the fuel consumption and emissions only at the upstream of the rarefaction wave while enhances the fuel consumption and emissions under other situations, which shows that the driver's bounded rationality has positive impacts on the fuel consumption and emissions only at the upstream of the rarefaction wave, while negative effects on the fuel consumption and emissions under other situations. In addition, the numerical results show that the driver's bounded rationality has little prominent impact on the total fuel consumption, and emissions during the whole evolution of small perturbation.
Impact of the Next-Nearest-Neighbor Interaction on Traffic Flow of Highway with Slopes
Institute of Scientific and Technical Information of China (English)
李志鹏; 周盈
2012-01-01
In this paper,we study the motion course of traffic flow on the slopes of a highway by applying a microscopic traffic model,which takes into account the next-nearest-neighbor interaction in an intelligent transportation system environment.Three common gradients of the highway,which are sag terrain,uphill terrain,and downhill terrain on a single-lane roadway,are selected to clarify the impact on the traffic flow by the next-nearest-neighbor interaction in relative velocity.We obtain the current-density relation for traffic flow on the sag,the uphill and the downhill under the next-nearest-neighbor interaction strategy.It is observed that the current saturates when the density is greater than a critical value and the current decreases when the density is greater than another critical value.When the density falls into the intermediate range between the two critical densities it is also found that the oscillatory jam,easily leads to traffic accidents,often appears in the downhill stage,and the next-nearest-neighbor interaction in relative velocity has a strong suppressing effect on this kind of dangerous congestion.A theoretical analysis is also presented to explain this important conclusion.
a Numerical Investigation of the Jamming Transition in Traffic Flow on Diluted Planar Networks
Achler, Gabriele; Barra, Adriano
In order to develop a toy model for car's traffic in cities, in this paper we analyze, by means of numerical simulations, the transition among fluid regimes and a congested jammed phase of the flow of kinetically constrained hard spheres in planar random networks similar to urban roads. In order to explore as timescales as possible, at a microscopic level we implement an event driven dynamics as the infinite time limit of a class of already existing model (Follow the Leader) on an Erdos-Renyi two-dimensional graph, the crossroads being accounted by standard Kirchoff density conservations. We define a dynamical order parameter as the ratio among the moving spheres versus the total number and by varying two control parameters (density of the spheres and coordination number of the network) we study the phase transition. At a mesoscopic level it respects an, again suitable, adapted version of the Lighthill-Whitham model, which belongs to the fluid-dynamical approach to the problem. At a macroscopic level, the model seems to display a continuous transition from a fluid phase to a jammed phase when varying the density of the spheres (the amount of cars in a city-like scenario) and a discontinuous jump when varying the connectivity of the underlying network.
Capacity of Freeway Merge Areas with Different On-Ramp Traffic Flow
Directory of Open Access Journals (Sweden)
Jinxing Shen
2015-06-01
Full Text Available This paper is aimed at investigating the influence of different types of traffic flows on the capacity of freeway merge areas. Based on the classical gap-acceptance model, two calculating models were established specifically considering randomly arriving vehicles and individual difference in driving behaviours. Monte-Carlo simulation was implemented to reproduce the maximum traffic volume on the designed freeway merge area under different situations. The results demonstrated that the proposed calculating models have better performance than the conventional gap-acceptance theory on accurately predicting the capacity of freeway merge areas. The findings of research could be helpful to improve the microscopic traffic flow simulation model from a more practical perspective and support the designing of freeway merge areas as well.
States of Traffic Flow in Deep Lefortovo Tunnel (Moscow): Empirical Data
Lubashevsky, I; Lifshits, B; Mahnke, R; Pechersky, M; Garnisov, Cyril; Lifshits, Boris; Lubashevsky, Ihor; Mahnke, Reinhard; Pechersky, Mikhail
2005-01-01
The paper presents a preliminary analysis of traffic flow data collected in the Lefortovo tunnel located on the 3-rd circular highway of Moscow. It is shown that the observed tunnel congested traffic in fact exhibits cooperative phenomena in vehicle motion, namely, there is a region of widely scatted states on the fundamental diagrams which is related typically to the appearance of synchronized traffic. Besides, the spatial autocorrelations in the occupancy, vehicle velocity, and flow rate measured by different detectors are found to be essential. Especially it concerns the correlations in the velocity and occupancy, their correlation length gets values about 1 km. The phase portrait of the vehicle ensemble dynamics on the occupancy-velocity plane is also studied. It is demonstrated that there are two substantially different region on it. One matches actually the cooperative vehicle motion and contains some kernel where the dynamics is pure chaotic. The other part of the phase plane corresponds to the irrever...
Rao, Anlei
2012-09-08
In a cognitive relay system, the secondary user is permitted to transmit data via a relay when licensed frequency bands are detected to be free. Previous studies mainly focus on reducing or limiting the interference of the secondary transmission on the primary users. On the other hand, however, the primary user traffic will also affect the data transmission performance of the secondary users. In this paper, we investigate the impact of the primary user traffic on the bit error rate (BER) of the secondary transmission, when the secondary user adopts adaptive transmission with a relay partially selected. From the numerical results, we can see that the primary user traffic seriously degrades average BER. The worse-link partial selection can perform almost as well as the global selection when the channel conditions of the source-relay links and the relay-destination links differ a lot. In addition, although the relay selection improves the spectral efficiency of the secondary transmission, numerical results show that it only has slight impact on the overall average BER, so that the robustness of the system will not be affected by the relay selection.
DEFF Research Database (Denmark)
Ganji, S.; Barari, Amin; Ibsen, Lars Bo
2012-01-01
In this paper we aim to find an analytical solution for jamming transition in traffic flow. Generally the Jamming Transition Problem (JTP) can be modeled via Lorentz system. So, in this way, the governing differential equation achieved is modeled in the form of a nonlinear damped oscillator...
Evolutionary air traffic flow management for large 3D-problems
Kemenade, C.H.M. van; Akker, J.M. van den; Kok, J.N.
1996-01-01
We present an evolutionary tool to solve free-route Air Traffic Flow Management problems within a three-dimensional air space. This is the first evolutionary tool which solves free-route planning problems involving a few hundred aircraft. We observe that the importance of the recombination operator
Equation-Free Analysis of Macroscopic Behavior in Traffic and Pedestrian Flow
DEFF Research Database (Denmark)
Marschler, Christian; Sieber, Jan; Hjorth, Poul G.;
2014-01-01
. This will facilitate a study of how the model behavior depends on parameter values including an understanding of transitions between different types of qualitative behavior. These methods are introduced and explained for traffic jam formation and emergence of oscillatory pedestrian counter flow in a corridor...
Two-dimensional cellular automaton model of traffic flow with open boundaries
Tadaki, S I
1996-01-01
A two-dimensional cellular automaton model of traffic flow with open boundaries are investigated by computer simulations. The outflow of cars from the system and the average velocity are investigated. The time sequences of the outflow and average velocity have flicker noises in a jamming phase. The low density behavior are discussed with simple jam-free approximation.
Directory of Open Access Journals (Sweden)
Zhenke Luo
2014-12-01
Full Text Available Mixed traffic flow composed of autos and non-autos widely exists in developing countries and areas. To investigate the operational characteristics of the mixed traffic flow consisting of vehicles in different types (large vehicles, cas, and bicycles, we develop a cellular automaton model to replicate the travel behaviors on a bi-directional road segment with respect to the physical and mechanic ftures of différent vehicle types. By implementing the eesential parameters calibrated through the field data collection, a numerical study is carried out considering the variation in volume, density, and velocity with different compositions of mixed traffic flows. The primary findings include: the average velocity of traffic flow and total volume decrease 60% and 30% after incorporating 10% bicycles, respectively; the phenomenon of double-summit in terms of the total volume appears when the proportion of bicycle is beyond 60%; the maximal total volume starts to recover when the proportion of bicycle is higher than 10 %.
di, Baofeng; Shi, Kai; Zhang, Kaishan; Svirchev, Laurence; Hu, Xiaoxi
2016-02-01
In this paper, a GIS-based method was developed to extract the real-time traffic information (RTTI) from the Google Maps system for city roads. The method can be used to quantify both congested and free-flow traffic conditions. The roadway length was defined as congested length (CL) and free-flow length (FFL). Chengdu, the capital of Sichuan Province in the southwest of China, was chosen as a case study site. The RTTI data were extracted from the Google real-time maps in May 12-17, 2013 and were used to derive the CL and FFL for the study areas. The Multifractal Detrended Fluctuation Analysis (MFDFA) was used to characterize the long-term correlations of CL and FFL time series and their corresponding multifractal properties. Analysis showed that CL and FFL had demonstrated time nonlinearity and long-term correlations and both characteristics differed significantly. A shuffling procedure and a phase randomization procedure were further integrated with multifractal detrending moving average (MFDMA) to identify the major sources of multifractality of these two time series. The results showed that a multifractal process analysis could be used to characterize complex traffic data. Traffic data collected and methods developed in this paper will help better understand the complex traffic systems.
COMPUTATION OF RETURN FLOWS DUE TO NAVIGATION TRAFFICS IN RESTRICTED WATERWAYS
Institute of Scientific and Technical Information of China (English)
B.S.MAZUMDER; S.K.DAS; S.N.DAS
2006-01-01
The paper deals with the development of an empirical model to compute the return flow due to the movement of navigation traffics in restricted waterway when the speed of the navigation traffic is under sub-critical range. The velocity profile of the return flow is modelled, where the functional dependence with respect to ambient flow, principal dimensions of the vessel, wetted cross-sectional area of the river, width and average depth of the river, and the lateral distance of the vessel from the bank are implicitly considered. This model has been validated with the observed data collected from the four specific sites, such as Kampsville, Apple River Island, Goose Island and Clarks Ferry of Illinois River during barge-tow movement. The present model shows significant improvement of return flow prediction in comparison to earlier empirical results. This model has also the ability to determine the locus of zero velocity point.
Traffic flow model at fixed control signals with discrete service time distribution
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Lucky I. Igbinosun
2016-04-01
Full Text Available Most of the models of road traffic flow at fixed-cycle controlled intersection assume stationary distributions and provide steady state results. The assumption that a constant number of vehicles can leave the system during the green phase is unrealistic in real life situations. A discrete time queuing model was developed to describe the operation of traffic flow at a road intersection with fixed-cycle signalized control and to account for the randomness in the number of vehicles that can leave the system. The results show the expected queue size in the system when the traffic is light and for a busy period, respectively. For the light period, when the traffic intensity is less than one, it takes a shorter green cycle time for vehicles to clear up than during high traffic intensity (the road junction is saturated. Increasing the number of cars that can leave the junction at the turn of the green phase reduces the number of cycle times before the queue is cleared.
ONE-DIMENSIONAL CELLULAR AUTOMATON MODEL OF TRAFFIC FLOW BASED ON CAR-FOLLOWING IDEA
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董力耘; 薛郁; 戴世强
2002-01-01
An improved one-dimensional CA (Cellular Automaton) traffic model was proposed to describe the highway traffic under the periodic boundary conditions. This model was based on the idea of the car-following model, which claims that the motion of a vehicle at one time step depends on both its headway and the synchronous motion of the front vehicle,thus including indirectly the influence of its sub-neighboring vehicle. In addition, the socalled safety distance was introduced to consider the deceleration behavior of vehicles and the stochastic factor was taken into account by introducing the deceleration probability.Meanwhile, the conditional deceleration in the model gives a better description of the phenomena observed on highways. It is found that there exists the metastability and hysteresis effect of traffic flow in the neighborhood of critical density under different initial conditions.Since this model gives a reasonable depiction of the motion of a single vehicle, it is easy to be extended to the case of traffic flow under the control of traffic lights in cities.
Adaptive Lattice Boltzmann Model for Compressible Flows
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
A new lattice Boltzmann model for compressible flows is presented. The main difference from the standard lattice Boltzmann model is that the particle velocities are no longer constant, but vary with the mean velocity and internal energy. The adaptive nature of the particle velocities permits the mean flow to have a high Mach number. The introduction of a particle potential energy makes the model suitable for a perfect gas with arbitrary specific heat ratio. The Navier-Stokes (N-S) equations are derived by the Chapman-Enskog method from the BGK Boltzmann equation. Two kinds of simulations have been carried out on the hexagonal lattice to test the proposed model. One is the Sod shock-tube simulation. The other is a strong shock of Mach number 5.09 diffracting around a corner.
Traffic Flow by Cellular Automata: the Effect of Maximal Car Velocity
Makowiecki, D S; Makowiec, Danuta; Miklaszewski, Wieslaw
2005-01-01
Effects of large value assigned to the maximal car velocity on the fundamental diagrams in the Nagel-Schreckenberg model are studied by extended simulations. The function relating the flow in the congested traffic phase with the car density and deceleration probability is found numerically. Properties of the region of critical changes, so-called jamming transition parameters, are described in details. The basic model, modified by the assumption that for each car an individual velocity limit is assigned, is investigated in the aim to find the best supplementary rule allowing the jammed traffic to move with velocity larger than the slowest driving vehicle.
New control strategy for the lattice hydrodynamic model of traffic flow
Zhu, Chenqiang; Zhong, Shiquan; Li, Guangyu; Ma, Shoufeng
2017-02-01
The new delayed-feedback control strategy is applied for lattice hydrodynamic model of traffic flow by considering the control signal of the variation rate of the optimal velocity. The linear stability condition is derived in the frequency-domain with control theory. Then, different feedback gains under the periodic boundary scenery and on-ramp scenery are simulated. The periodic boundary scenery provides an initial small disturbance situation on the circle road, while the on-ramp scenery reproduces the disturbance triggered by the on-ramp on the open road. Both the theoretical analysis and simulations show that this new control signal has a positive effect to suppress traffic jams.
Effect of the Length of Traffic Flow Records on the Estimate of a Bridge Service Life
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Krejsa Jan
2016-12-01
Full Text Available The service life of bridges is significantly affected by fatigue of used material induced by heavy vehicles. Therefore, precise determination of the vehicle weight is of crucial importance for the calculation of fatigue damage and the prediction of the bridge serviceability. This paper investigates accuracy of the determination of fatigue depending on the length of traffic flow recording. The presented data were obtained from the measurements carried out on a bridge of the Prague Highway Ring. The analysis reveals that the optimal length of traffic recording is about 30 days.
Analytical and grid-free solutions to the Lighthill-Whitham-Richards traffic flow model
Mazaré, Pierre Emmanuel
2011-12-01
In this article, we propose a computational method for solving the Lighthill-Whitham-Richards (LWR) partial differential equation (PDE) semi-analytically for arbitrary piecewise-constant initial and boundary conditions, and for arbitrary concave fundamental diagrams. With these assumptions, we show that the solution to the LWR PDE at any location and time can be computed exactly and semi-analytically for a very low computational cost using the cumulative number of vehicles formulation of the problem. We implement the proposed computational method on a representative traffic flow scenario to illustrate the exactness of the analytical solution. We also show that the proposed scheme can handle more complex scenarios including traffic lights or moving bottlenecks. The computational cost of the method is very favorable, and is compared with existing algorithms. A toolbox implementation available for public download is briefly described, and posted at http://traffic.berkeley.edu/project/downloads/lwrsolver. © 2011 Elsevier Ltd.
Characteristics of traffic flow at nonsignalized T-shaped intersection with U-turn movements.
Fan, Hong-Qiang; Jia, Bin; Li, Xin-Gang; Tian, Jun-Fang; Yan, Xue-Dong
2013-01-01
Most nonsignalized T-shaped intersections permit U-turn movements, which make the traffic conditions of intersection complex. In this paper, a new cellular automaton (CA) model is proposed to characterize the traffic flow at the intersection of this type. In present CA model, new rules are designed to avoid the conflicts among different directional vehicles and eliminate the gridlock. Two kinds of performance measures (i.e., flux and average control delay) for intersection are compared. The impacts of U-turn movements are analyzed under different initial conditions. Simulation results demonstrate that (i) the average control delay is more practical than flux in measuring the performance of intersection, (ii) U-turn movements increase the range and degree of high congestion, and (iii) U-turn movements on the different direction of main road have asymmetrical influences on the traffic conditions of intersection.
Characteristics of Traffic Flow at Nonsignalized T-Shaped Intersection with U-Turn Movements
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Hong-Qiang Fan
2013-01-01
Full Text Available Most nonsignalized T-shaped intersections permit U-turn movements, which make the traffic conditions of intersection complex. In this paper, a new cellular automaton (CA model is proposed to characterize the traffic flow at the intersection of this type. In present CA model, new rules are designed to avoid the conflicts among different directional vehicles and eliminate the gridlock. Two kinds of performance measures (i.e., flux and average control delay for intersection are compared. The impacts of U-turn movements are analyzed under different initial conditions. Simulation results demonstrate that (i the average control delay is more practical than flux in measuring the performance of intersection, (ii U-turn movements increase the range and degree of high congestion, and (iii U-turn movements on the different direction of main road have asymmetrical influences on the traffic conditions of intersection.
A traffic flow cellular automaton model to considering drivers' learning and forgetting behaviour
Institute of Scientific and Technical Information of China (English)
Ding Jian-Xun; Huang Hai-Jun; Tian Qiong
2011-01-01
It is known that the commonly used NaSch cellular automaton (CA) model and its modifications can help explain the internal causes of the macro phenomena of traffic flow. However, the randomization probability of vehicle velocity used in these models is assumed to be an exogenous constant or a conditional constant, which cannot reflect the learning and forgetting behaviour of drivers with historical experiences. This paper further modifies the NaSch model by enabling the randomization probability to be adjusted on the bases of drivers' memory. The Markov properties of this modified model are discussed. Analytical and simulation results show that the traffic fundamental diagrams can be indeed improved when considering drivers' intelligent behaviour. Some new features of traffic are revealed by differently combining the model parameters representing learning and forgetting behaviour.
A heterogeneous traffic flow model consisting of two types of vehicles with different sensitivities
Li, Zhipeng; Xu, Xun; Xu, Shangzhi; Qian, Yeqing
2017-01-01
A heterogeneous car following model is constructed for traffic flow consisting of low- and high-sensitivity vehicles. The stability criterion of new model is obtained by using the linear stability theory. We derive the neutral stability diagram for the proposed model with five distinct regions. We conclude the effect of the percentage of low-sensitivity vehicle on the traffic stability in each region. In addition, we further consider a special case that the number of the low-sensitivity vehicles is equal to that of the high-sensitivity ones. We explore the dependence of traffic stability on the average value and the standard deviation of two sensitivities characterizing two vehicle types. The direct numerical simulation results verify the conclusion of theoretical analysis.
Cellular Automaton Models of Highway Traffic Flow Considering Lane-Control and Speed-Control
Institute of Scientific and Technical Information of China (English)
钱勇生; 李文俊; 曾俊伟; 王敏; 杜加伟; 广晓平
2011-01-01
As two kinds of management modes of highway tramc control, lane-control, and speed-control produce different effect under different conditions. In this paper, traffic flow cellular automaton models for four-lane highway system with two opposing directions under the above two modes are established considering car and truck mixed running. Through computer numerical simulating, the fundamental diagrams with different parameters are obtained, and after the analysis of density-flux diagrams, the variation discipline of flux with traffic density under different control models is gained. The results indicate that, compared with lane-control, utilization ratio of road can be further improved with speed-control when the truck number increases. The research result is of great significance for reasonable providing theoretical guidance for highway traffic control.
Possible Self-Organised Criticality and Dynamical Clustering of Traffic flow in Open Systems
Larraga, M E; Mehta, A; Mehta, Anita
1999-01-01
We focus in this work on the study of traffic in open systems using a modified version of an existing cellular automaton model. We demonstrate that the open system is rather different from the closed system in its 'choice' of a unique steady-state density and velocity distribution, independently of the initial conditions, reminiscent of self-organised criticality. Quantities of interest such as average densities and velocities of cars, exhibit phase transitions between free flow and the jammed state, as a function of the braking probability R in a way that is very different from closed systems. Velocity correlation functions show that the concept of a dynamical cluster, introduced earlier in the context of granular flow is also relevant for traffic flow models.
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Wei Xu
2015-01-01
Full Text Available Traditionally, to implement the first-best marginal cost pricing scheme in a traffic network requires the information on the exact demand function or true origin-destination demand, which, however, is rarely available in practice. To overcome this dilemma, the trial-and-error method has been proposed to find the marginal cost toll through an iterative process using the observed traffic volumes. This method guarantees the convergence of tolls and flows to the system optimal state under the assumption of deterministic traffic conditions. However, in reality, the uncertainty of transportation network has been recognized well that induces the variability of link flow and travel time. Therefore, this paper proposes an evolutionary implementation method that iteratively finds the first-best marginal cost toll pattern according to the observed stochastic link flow information and the known travel time functions. The proof of the convergence of the iterative algorithm is presented. The paper also analyzes the effect of the sampling error of the link flow data on the convergence of the algorithm and shows that the biases from the flow observation will not affect the convergence. The numerical tests are provided for the illustration of the algorithm.
Space-time correlation analysis of traffic flow on road network
Su, Fei; Dong, Honghui; Jia, Limin; Tian, Zhao; Sun, Xuan
2017-02-01
Space-time correlation analysis has become a basic and critical work in the research on road traffic congestion. It plays an important role in improving traffic management quality. The aim of this research is to examine the space-time correlation of road networks to determine likely requirements for building a suitable space-time traffic model. In this paper, it is carried out using traffic flow data collected on Beijing’s road network. In the framework, the space-time autocorrelation function (ST-ACF) is introduced as global measure, and cross-correlation function (CCF) as local measure to reveal the change mechanism of space-time correlation. Through the use of both measures, the correlation is found to be dynamic and heterogeneous in space and time. The finding of seasonal pattern present in space-time correlation provides a theoretical assumption for traffic forecasting. Besides, combined with Simpson’s rule, the CCF is also applied to finding the critical sections in the road network, and the experiments prove that it is feasible in computability, rationality and practicality.
A novel macro model of traffic flow with the consideration of anticipation optimal velocity
Peng, G. H.; Song, W.; Peng, Y. J.; Wang, S. H.
2014-03-01
In this paper, a novel macro model which can investigate wide moving jams is derived from car-following model by applying the relationship between the micro and macro variables with the consideration of anticipation optimal velocity on single lane. The theoretic analysis and numerical simulation show that the new macro model of traffic flow can correctly reproduce common evolution of shock, rarefaction wave and local cluster effect under small perturbation, which shows that the congested traffic patterns about wide moving jam propagation are in accordance with empirical results. Furthermore, the results uncover that the anticipation effect can smooth the front of the shock wave and the rarefaction wave, which means that anticipation effect hasten the diffusion process of congregate in the shock wave and dissolution in rarefaction wave. The key improvement of this new macro model over the previous ones lies in the fact that the anticipation traffic behaviors can improve the stability of traffic flow with the consideration of the proper anticipation effect.
Highly Dynamic and Adaptive Traffic Congestion Avoidance in Real-Time Inspired by Honey Bee Behavior
Wedde, Horst F.; Lehnhoff, Sebastian; van Bonn, Bernhard; Bay, Z.; Becker, S.; Böttcher, S.; Brunner, C.; Büscher, A.; Fürst, T.; Lazarescu, A. M.; Rotaru, E.; Senge, S.; Steinbach, B.; Yilmaz, F.; Zimmermann, T.
Traffic congestions have become a major problem in metropolitan areas world-wide, within and between cities, to an extent where they make driving and transportation times largely unpredictable. Due to the highly dynamic character of congestion building and dissolving this phenomenon appears even to resist a formal treatment. Static approaches, and even more their global management, have proven counterproductive in practice. Given the latest progress in VANET technology and the remarkable commercially driven efforts like in the European C2C consortium, or the VSC Project in the US, allow meanwhile to tackle various aspects of traffic regulation through VANET communication. In this paper we introduce a novel, completely decentralized multi-agent routing algorithm (termed BeeJamA) which we have derived from the foraging behavior of honey bees. It is highly dynamic, adaptive, robust, and scalable, and it allows for both avoiding congestions, and minimizing traveling times to individual destinations. Vehicle guidance is provided well ahead of every intersection, depending on the individual speeds. Thus strict deadlines are imposed on, and respected by, the BeeJamA algorithm. We report on extensive simulation experiments which show the superior performance of BeeJamA over conventional approaches.
关于交通成本演化方程的假设及经济分析%Economic Analysis of Traffic Flow with an Evolution Equation
Institute of Scientific and Technical Information of China (English)
FENG Su-wei
2005-01-01
Based on two main hypotheses of traffic economical equilibrium and the relationship between traffic density and the demand,an evolution equation of traffic cost was proposed to describe the change of cost under decreasing toll. Economical explanation of the model and a numerical case were given to demonstrate the constraint between the marginal traffic demand and the flow velocity.
Cheng, Anyu; Jiang, Xiao; Li, Yongfu; Zhang, Chao; Zhu, Hao
2017-01-01
This study proposes a multiple sources and multiple measures based traffic flow prediction algorithm using the chaos theory and support vector regression method. In particular, first, the chaotic characteristics of traffic flow associated with the speed, occupancy, and flow are identified using the maximum Lyapunov exponent. Then, the phase space of multiple measures chaotic time series are reconstructed based on the phase space reconstruction theory and fused into a same multi-dimensional phase space using the Bayesian estimation theory. In addition, the support vector regression (SVR) model is designed to predict the traffic flow. Numerical experiments are performed using the data from multiple sources. The results show that, compared with the single measure, the proposed method has better performance for the short-term traffic flow prediction in terms of the accuracy and timeliness.
A two-lane cellular automaton traffic flow model with the influence of driver, vehicle and road
Zhao, Han-Tao; Nie, Cen; Li, Jing-Ru; Wei, Yu-Ao
2016-07-01
On the basis of one-lane comfortable driving model, this paper established a two-lane traffic cellular automata model, which improves the slow randomization effected by brake light. Considering the driver psychological characteristics and mixed traffic, we studied the lateral influence between vehicles on adjacent lanes. Through computer simulation, the space-time diagram and the fundamental figure under different conditions are obtained. The study found that aggressive driver makes a slight congestion in low-density traffic and improves the capacity of high-density traffic, when the density exceeds 20pcu/km the more aggressive drivers the greater the flow, when the density below 40pcu/km driver character makes an effect, the more cautious driver, the lower the flow. The ratio of big cars has the same effect as the ratio of aggressive drivers. Brake lights have the greatest impact on traffic flow and when the density exceeds 10pcu/km the traffic flow fluctuates. Under periodic boundary conditions, the disturbance of road length on traffic is minimal. The lateral influence only play a limited role in the medium-density conditions, and only affect the average speed of traffic at low density.
Institute of Scientific and Technical Information of China (English)
ZHANG Lei; SONG Tiecheng; WU Ming; BAO Xu; GUO Jie; HU Jing
2015-01-01
In order to meet diff erent delay require-ments of various communication services in Cognitive ra-dio (CR) networks, Secondary users (SUs) are divided into two classes according to the priority of accessing to spec-trum in this paper. Based on the proactive spectrum hand-off scheme, the Preemptive resume priority (PRP) M/G/1 queueing is used to characterize multiple spectrum hand-off s under two diff erent spectrum handoff strategies. The traffic-adaptive spectrum handoff strategy is proposed for graded SUs so as to minimize the average cumulative hand-off delay. Simulation results not only verify that our theo-retical analysis is valid, but also show that the strategy we proposed can reduce the average cumulative handoff delay evidently. The eff ect of service rate on the proposed spec-trum switching point and the admissible access region are provided.
ANALYSIS OF THE STRUCTURAL PROPERTIES OF THE SOLUTIONS TO SPEED GRADIENT TRAFFIC FLOW MODEL
Institute of Scientific and Technical Information of China (English)
JIANG Rui; WU Qingsong
2004-01-01
In this paper, we carry out an analysis of the structural properties of the solutions to the speed gradient (SG) traffic flow model. Under the condition that the relaxation effect can be neglected, it is shown that a 1-shock or a 1-rarefaction is associated with the first characteristic, but on the other hand, a contact discontinuity rather than a 2-shock or a 2-rarefaction is associated with the second characteristic. Since the existence of a 2-shock or 2-rarefaction violates the physical mechanism of the traffic flow, the SG model is more reasonable. If the relaxation effect cannot be neglected, it is somewhat difficult to carry out the analytical analysis and the numerical simulation results should be obtained.
Optimal proportion of studded tyres in traffic flow to prevent polishing of an icy road.
Tuononen, Ari J; Sainio, Panu
2014-04-01
Studded tyres can significantly wear the road surface and increase particle emissions from the road surface, which has a negative impact on air quality in urban areas. However, road wear might have a positive aspect by roughening the road surface and thus preventing polishing. As a consequence, other vehicles than the ones using studded tyres might also benefit from the usage of studded tyres. The impact of the proportion of studded tyres in the traffic flow on the tyre-ice friction coefficient was studied with a fleet of real cars in a closed environment under strict procedural control. The results show that a proportion of 25-50% studded tyres in the traffic flow is enough to prevent ice from developing in a manner that is critically slippery for non-studded winter tyres. It was also observed that the visual appearance of the ice surface does not indicate if the ice has become more slippery or not.
Gonzalez-Feliu, Jesus; Henriot, Frédéric; Routhier, Jean-Louis
2009-01-01
We present an integrated transport and land-use model for prediction of traffic flows for the entire urban logistics system. The model shows the relation between several aspects of commercial strategies (store location, commercial area's supply, and urban planning policies) and both the upstream distribution of goods and the downstream usage of private vehicles for shopping. Several case studies based on representative scenarios are proposed.
Upper bounds for the critical car densities in traffic flow problems
Chau, H F; Woo, Y F; Chau, H F; Hui, P M; Woo, Y F
1995-01-01
In most models of traffic flow, the car density p is the only free parameter in determining the average car velocity \\langle v \\rangle. The critical car density p_c, which is defined to be the car density separating the jamming phase (with \\langle v \\rangle = 0) and the moving phase (with \\langle v \\rangle > 0), is an important physical quantity to investigate. By means of simple statistical argument, we show that p_c 2) dimensions.
Roads at risk: traffic detours from debris flows in southern Norway
Meyer, N. K.; Schwanghart, W.; Korup, O.; Nadim, F.
2015-05-01
Globalisation and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g. road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load, expressed as vehicle kilometres, because of debris-flow-related road closures. We present two scenarios demonstrating the impact of debris flows on the road network and quantify the associated path-failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and north-western part of the study area are associated with high link-failure risk. Yet options for detours on major routes are manifold and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying on speedy delivery of services and goods.
Roads at risk – traffic detours from debris flows in southern Norway
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N. K. Meyer
2014-10-01
Full Text Available Globalization and interregional exchange of people, goods, and services has boosted the importance of and reliance on all kinds of transport networks. The linear structure of road networks is especially sensitive to natural hazards. In southern Norway, steep topography and extreme weather events promote frequent traffic disruption caused by debris flows. Topographic susceptibility and trigger frequency maps serve as input into a hazard appraisal at the scale of first-order catchments to quantify the impact of debris flows on the road network in terms of a failure likelihood of each link connecting two network vertices, e.g., road junctions. We compute total additional traffic loads as a function of traffic volume and excess distance, i.e. the extra length of an alternative path connecting two previously disrupted network vertices using a shortest-path algorithm. Our risk metric of link failure is the total additional annual traffic load expressed as vehicle kilometers because of debris-flow related road closures. We present two scenarios demonstrating the impact of debris flows on the road network, and quantify the associated path failure likelihood between major cities in southern Norway. The scenarios indicate that major routes crossing the central and northwestern part of the study area are associated with high link failure risk. Yet options for detours on major routes are manifold, and incur only little additional costs provided that drivers are sufficiently well informed about road closures. Our risk estimates may be of importance to road network managers and transport companies relying of speedy delivery of services and goods.
Car-following theory of steady-state traffic flow using time-to-collision
Institute of Scientific and Technical Information of China (English)
Sheng JIN; Zhi-yi HUANG; Peng-fei TAO; Dian-hai WANG
2011-01-01
The conventional car-following theory is based on the assumption that vehicles will travel along the center line of lanes.However,according to the field survey data,in complex traffic conditions,a lateral separation between the leader and the follower frequently occurs.Accordingly,by taking lateral separation into account,we redefined the equation of time-to-collision (TTC) using visual angle information.Based on the stimulus-response framework,TTC was introduced into the basic General Motors (GM) model as a stimulus,and a non-lane-based car-following model of steady-state traffic flow was developed.The property of flow-density relationship was further investigated after integrating the proposed car-following model with different parameters.The results imply that the property of steady-state traffic flow and the capacity of each lane are highly relevant to the microscopic staggered car-following behavior,and the proposed model significantly enhances the practicality of the human driving behavior model.
Ren, Yihui
As real-world complex networks are heterogeneous structures, not all their components such as nodes, edges and subgraphs carry the same role or importance in the functions performed by the networks: some elements are more critical than others. Understanding the roles of the components of a network is crucial for understanding the behavior of the network as a whole. One the most basic function of networks is transport; transport of vehicles/people, information, materials, forces, etc., and these quantities are transported along edges between source and destination nodes. For this reason, network path-based importance measures, also called centralities, play a crucial role in the understanding of the transport functions of the network and the network's structural and dynamical behavior in general. In this thesis we study the notion of betweenness centrality, which measures the fraction of lowest-cost (or shortest) paths running through a network component, in particular through a node or an edge. High betweenness centrality nodes/edges are those that will be frequently used by the entities transported through the network and thus they play a key role in the overall transport properties of the network. In the first part of the thesis we present a first-principles based method for traffic prediction using a cost-based generalization of the radiation model (emission/absorbtion model) for human mobility, coupled with a cost-minimizing algorithm for efficient distribution of the mobility fluxes through the network. Using US census and highway traffic data, we show that traffic can efficiently and accurately be computed from a range-limited, network betweenness type calculation. The model based on travel time costs captures the log-normal distribution of the traffic and attains a high Pearson correlation coefficient (0.75) when compared with real traffic. We then focus on studying the extent of changes in traffic flows in the wake of a localized damage or alteration to the
Predicting Traffic Flow in Local Area Networks by the Largest Lyapunov Exponent
Directory of Open Access Journals (Sweden)
Yan Liu
2016-01-01
Full Text Available The dynamics of network traffic are complex and nonlinear, and chaotic behaviors and their prediction, which play an important role in local area networks (LANs, are studied in detail, using the largest Lyapunov exponent. With the introduction of phase space reconstruction based on the time sequence, the high-dimensional traffic is projected onto the low dimension reconstructed phase space, and a reduced dynamic system is obtained from the dynamic system viewpoint. Then, a numerical method for computing the largest Lyapunov exponent of the low-dimensional dynamic system is presented. Further, the longest predictable time, which is related to chaotic behaviors in the system, is studied using the largest Lyapunov exponent, and the Wolf method is used to predict the evolution of the traffic in a local area network by both Dot and Interval predictions, and a reliable result is obtained by the presented method. As the conclusion, the results show that the largest Lyapunov exponent can be used to describe the sensitivity of the trajectory in the reconstructed phase space to the initial values. Moreover, Dot Prediction can effectively predict the flow burst. The numerical simulation also shows that the presented method is feasible and efficient for predicting the complex dynamic behaviors in LAN traffic, especially for congestion and attack in networks, which are the main two complex phenomena behaving as chaos in networks.
Tampere, C.M.J.; Hoogendoorn, S.P.; Arem, B. van
2009-01-01
This paper presents a continuous traffic-flow model for the explorative analysis of advanced driver-assistance systems (ADASs). Such systems use technology (sensors and intervehicle communication) to support the task of the driver, who retains full control over the vehicle. Based on a review of diff
Numerical analysis on car-following traffic flow models with delay time
Institute of Scientific and Technical Information of China (English)
LI Li; SHI Peng-fei
2006-01-01
Effects of the speed relaxation time on the optimal velocity car-following model (OVM) with delay time due to driver reaction time proposed by Bando et al.(1995) were studied by numerical methods. Results showed that the OVM including the delay is not physically sensitive to the speed relaxation times. A modified car-following model is proposed to overcome the deficiency. Analyses of the linear stability of the modified model were conducted. It is shown that coexisting flows appear ifthe initial homogeneous headway of the traffic flow is between critical values. In addition, phase transitions occur on varying the initially homogeneous headway.
Tam, Johnny; Tiruveedhula, Pavan; Roorda, Austin
2011-03-02
Adaptive Optics Scanning Laser Ophthalmoscopy was used to noninvasively acquire videos of single-file flow through live human retinal parafoveal capillaries. Videos were analyzed offline to investigate capillary flow dynamics. Certain capillaries accounted for a clear majority of leukocyte traffic (Leukocyte-Preferred-Paths, LPPs), while other capillaries primarily featured plasma gap flow (Plasma-Gap-Capillaries, PGCs). LPPs may serve as a protective mechanism to prevent inactivated leukocytes from entering exchange capillaries, and PGCs may serve as relief valves to minimize flow disruption due to the presence of a leukocyte in a neighboring LPP.
Institute of Scientific and Technical Information of China (English)
谢溪凌; 肖建波; 张昊; 谭玉莹; 倪明安; 刘阳; 张志富; 郑卫刚
2012-01-01
An intelligent optimization system was developed in consideration of traffic light operating states and time traffic flow to save energy and alleviate the pressure on the urban traffic in Wuhan, China. Since Wuhan's traffic light working time is relatively fixed, the system uses detecting apparatus to monitor the traffic on the road and then feedbacks collected signals to the microcontroller control system. Adaptive intelligent traffic lights were designed based on the existing traffic light control equipments in Wuhan, with content networking technologies being used and particle swarm optimization being achieved using Matlab software. The results show that the particle swarm optimization algorithm reduces the average vehicle traffic time by 20% compared with the Webster algorithm, with the vehicle idle time reduced and the idle oil consumption saved.%为了节能减排并缓解中国武汉城市交通压力，设计了一种考虑时段交通流交通灯工作状态智能优化系统。针对目前武汉市交通灯的各个状态的工作时间相对固定的缺陷，利用检测装置，监测道路上的车流量，并反馈给单片机控制系统。在不改变武汉市原有交通灯控制设备的基础上，制作出一种随车流量的改变而改变通行时间的智能交通灯，并且融入物联网技术，采用了Matlab实现粒子群算法优化，进行优化设计，即根据实时交通状况灵活地改变切换交通灯的工作状态。结果表明：与Webster算法比较，粒子群优化算法计算的车辆通行时间平均减少20％。因此，可减小车辆的怠速时间，节约怠速油耗。
Li, Zhipeng; Xu, Xun; Xu, Shangzhi; Qian, Yeqing; Xu, Juan
2016-07-01
The car-following model is extended to take into account the characteristics of mixed traffic flow containing fast and slow vehicles. We conduct the linear stability analysis to the extended model with finding that the traffic flow can be stabilized with the increase of the percentage of the slow vehicle. It also can be concluded that the stabilization of the traffic flow closely depends on not only the average value of two maximum velocities characterizing two vehicle types, but also the standard deviation of the maximum velocities among all vehicles, when the percentage of the slow vehicles is the same as that of the fast ones. With increase of the average maximum velocity, the traffic flow becomes more and more unstable, while the increase of the standard deviation takes negative effect in stabilizing the traffic system. The direct numerical results are in good agreement with those of theoretical analysis. Moreover, the relation between the flux and the traffic density is investigated to simulate the effects of the percentage of slow vehicles on traffic flux in the whole density regions.
Self-Organization in 2D Traffic Flow Model with Jam-Avoiding Drive
Nagatani, Takashi
1995-04-01
A stochastic cellular automaton (CA) model is presented to investigate the traffic jam by self-organization in the two-dimensional (2D) traffic flow. The CA model is the extended version of the 2D asymmetric exclusion model to take into account jam-avoiding drive. Each site contains either a car moving to the up, a car moving to the right, or is empty. A up car can shift right with probability p ja if it is blocked ahead by other cars. It is shown that the three phases (the low-density phase, the intermediate-density phase and the high-density phase) appear in the traffic flow. The intermediate-density phase is characterized by the right moving of up cars. The jamming transition to the high-density jamming phase occurs with higher density of cars than that without jam-avoiding drive. The jamming transition point p 2c increases with the shifting probability p ja. In the deterministic limit of p ja=1, it is found that a new jamming transition occurs from the low-density synchronized-shifting phase to the high-density moving phase with increasing density of cars. In the synchronized-shifting phase, all up cars do not move to the up but shift to the right by synchronizing with the move of right cars. We show that the jam-avoiding drive has an important effect on the dynamical jamming transition.
Dilemma game structure observed in traffic flow at a 2-to-1 lane junction.
Yamauchi, Atsuo; Tanimoto, Jun; Hagishima, Aya; Sagara, Hiroki
2009-03-01
Using a cellular automaton traffic model based on the stochastic optimal velocity model with appropriate assumptions for both incoming and outgoing vehicle boundaries, the so-called bottleneck issue on a lane-closing section was investigated in terms of game theory. In the system, two classified driver agents coexist: C agents (cooperative strategy) always driving in the first lane and D agents (defective strategy) trying to drive in a lower-density lane whether the first or the second lane. In high-density flow, D agents' interruption into the first lane from the second just before the lane-closing section creates a heavier traffic jam, which reduces social efficiency. This particular event can be described with a prisoner's dilemma game structure.
Study on effect of toll station on the traffic flow on three-line road
Wang, Guang-yu; Li, Wen-bo; Feng, Yu-jie
2013-03-01
Based on the NaSch Model, a new three-line cellular automata model emphasizing toll station on the high ways is built to discuss the impact of different amount of toll stations on the traffic flow. The models are as follows: Firstly, the process of cars driving is simulated. Secondly, the process of pulling station is simulated. In this part, two Cellular Automata Models are built separately for two cases, three tollbooths in the toll station and four tollbooths. The result shows that when the density of cars is on medium level, comparing with the toll station with three tollbooths, the toll station with four tollbooths can remit the traffic congestion effectively, but when the density of cars is too high or too low, the toll station with three tollbooths can do better.
On the micro-to-macro limit for first-order traffic flow models on networks
Cristiani, Emiliano
2015-01-01
Connections between microscopic follow-the-leader and macroscopic fluid-dynamics traffic flow models are already well understood in the case of vehicles moving on a single road. Analogous connections in the case of road networks are instead lacking. This is probably due to the fact that macroscopic traffic models on networks are in general ill-posed, since the conservation of the mass is not sufficient alone to characterize a unique solution at junctions. This ambiguity makes more difficult to find the right limit of the microscopic model, which, in turn, can be defined in different ways near the junctions. In this paper we show that a natural extension of the first-order follow-the-leader model on networks corresponds, as the number of vehicles tends to infinity, to the LWR-based multi-path model introduced in [Bretti et al., Discrete Contin. Dyn. Syst. Ser. S, 7 (2014)] and [Briani and Cristiani, Netw. Heterog. Media, 9 (2014)].
Shi, Xiao-Qiu; Wu, Yi-Qi; Li, Hong; Zhong, Rui
2007-11-01
Two-dimensional cellular automaton model has been broadly researched for traffic flow, as it reveals the main characteristics of the traffic networks in cities. Based on the BML models, a first-order phase transition occurs between the low-density moving phase in which all cars move at maximal speed and the high-density jammed phase in which all cars are stopped. However, it is not a physical result of a realistic system. We propose a new traffic rule in a two-dimensional traffic flow model containing road sections, which reflects that a car cannot enter into a road crossing if the road section in front of the crossing is occupied by another car. The simulation results reveal a second-order phase transition that separates the free flow phase from the jammed phase. In this way the system will not be entirely jammed (“don’t block the box” as in New York City).
Institute of Scientific and Technical Information of China (English)
Chung-Yung Wang; Jia-Wun Zhang
2014-01-01
This study focuses on estimating O-D （origin-destination） trip demand from link traffic flows. Equality relationship among link traffic flow, path flow, and O-D trip matrices are used to establish a linear equation system. Solution characteristics are analyzed based on the relationship between the rank of the link/path incidence matrix and column variables. And under the solution framework of conditional inverse matrices, a column exchange method and a path flow proportion method have been developed. Network testing results verify that the proposed methods yield good results.
基于车流量的交通灯控制系统设计%Traffic Light Control System Design Based on Traffic Flow
Institute of Scientific and Technical Information of China (English)
章伟; 张代远
2015-01-01
As traffic congestion rises within urban around the world,the intelligent control of traffic signals within cities is becoming in-creasingly important. Previous research for the area of intelligent traffic signal control has several shortcomings,including a reliance on historical data,fixing timing,not solving complicated and changeable situation. Propose the intelligent traffic lights control system based on traffic flow in this paper. It can get real-time traffic information with the help of video detection technology,and design the time algo-rithm that based on the information measured to adjust the control of the time of green light in all lanes,which can accurately change the time of traffic lights by achieving traffic dynamic adjustment. This solution allows signals to be updated frequently to match current traffic demand. It can alleviate traffic pressure,improve efficiency,save people's time and energy and protect the environment.%随着在世界各地交通拥堵现象日趋严重，城市内的交通信号智能控制变得越来越重要。先前研究的智能交通信号控制领域内有几个缺点，包括：依赖历史数据、固定配时、不能解决现实复杂多变的环境。文中提出的基于车流量的智能交通灯控制系统，利用视频检测技术，测得路口的实时车流信息，并依据所测得的信息设计了时间分配控制算法来调整控制各车道的绿灯时间，实时改变交通灯的时长以实现车流动态调节，该方案允许信号实时被更新以匹配当前的交通需求。运用到实际可达到缓解交通压力、提高通行效率、节省出行时间、节能减排、保护环境的目的。
Adaptive methods in computational fluid dynamics of chemically reacting flows
Rogg, B.
1991-09-01
Possible approaches to fully implicit adaptive algorithms suitable for the numerical simulation of unsteady two-dimensional reactive flows are examined. Emphasis is placed on self-adaptive gridding procedures applicable to time-dependent two-dimensional reactive flows. Pulsating flame propagation, autoignition in a nonpremixed flow, flame propagation in a strained mixing layer, and hot-spot-like self-ignition are considered as examples.
A two-stage short-term traffic flow prediction method based on AVL and AKNN techniques
Institute of Scientific and Technical Information of China (English)
孟梦; 王博彬; 邵春福; 李慧轩; 黃育兆
2015-01-01
Short-term traffic flow prediction is one of the essential issues in intelligent transportation systems (ITS). A new two-stage traffic flow prediction method named AKNN-AVL method is presented, which combines an advancedk-nearest neighbor (AKNN) method and balanced binary tree (AVL) data structure to improve the prediction accuracy. The AKNN method uses pattern recognition two times in the searching process, which considers the previous sequences of traffic flow to forecast the future traffic state. Clustering method and balanced binary tree technique are introduced to build case database to reduce the searching time. To illustrate the effects of these developments, the accuracies performance of AKNN-AVL method,k-nearest neighbor (KNN) method and the auto-regressive and moving average (ARMA) method are compared. These methods are calibrated and evaluated by the real-time data from a freeway traffic detector near North 3rd Ring Road in Beijing under both normal and incident traffic conditions. The comparisons show that the AKNN-AVL method with the optimal neighbor and pattern size outperforms both KNN method and ARMA method under both normal and incident traffic conditions. In addition, the combinations of clustering method and balanced binary tree technique to the prediction method can increase the searching speed and respond rapidly to case database fluctuations.
Li, Xin; Li, Xingang; Xiao, Yao; Jia, Bin
2016-06-01
Real traffic is heterogeneous with car and truck. Due to mechanical restrictions, the car and the truck have different limited deceleration capabilities, which are important factors in safety driving. This paper extends the single lane safety driving (SD) model with limited deceleration capability to two-lane SD model, in which car-truck heterogeneous traffic is considered. A car has a larger limited deceleration capability while a heavy truck has a smaller limited deceleration capability as a result of loaded goods. Then the safety driving conditions are different as the types of the following and the leading vehicles vary. In order to eliminate the well-known plug in heterogeneous two-lane traffic, it is assumed that heavy truck has active deceleration behavior when the heavy truck perceives the forming plug. The lane-changing decisions are also determined by the safety driving conditions. The fundamental diagram, spatiotemporal diagram, and lane-changing frequency were investigated to show the effect of mechanical restriction on heterogeneous traffic flow. It was shown that there would be still three traffic phases in heterogeneous traffic condition; the active deceleration of the heavy truck could well eliminate the plug; the lane-changing frequency was low in synchronized flow; the flow and velocity would decrease as the proportion of heavy truck grows or the limited deceleration capability of heavy truck drops; and the flow could be improved with lane control measures.
Jian, Mei-Ying; Shi, Jing; Liu, Yang
2016-09-01
As the global population ages, there are more and more older drivers on the road. The decline in driving performance of older drivers may influence the properties of traffic flow and safety. The purpose of this paper is to investigate the effect of older drivers’ driving behaviors on traffic flow. A modified cellular automaton (CA) model which takes driving behaviors of older drivers into account is proposed. The simulation results indicate that older drivers’ driving behaviors induce a reduction in traffic flow especially when the density is higher than 15 vehicles per km per lane and an increase in Lane-changing frequency. The analysis of stability shows that a number of disturbances could frequently emerge, be propagated and eventually dissipate in this modified model. The results also reflect that with the increase of older drivers on the road, the probability of the occurrence of rear-end collisions increases greatly and obviously. Furthermore, the value of acceleration influences the traffic flow and safety significantly. These results provide the theoretical basis and reference for the traffic management departments to develop traffic management measure in the aging society.
Institute of Scientific and Technical Information of China (English)
Sun Di-Hua; Peng Guang-Han
2009-01-01
In this paper,the viscous continuum traffic flow model for a single lane is extended to the traffic flow for two-lane freeways. The proposed model is a higher-order continuum model considering the coupling and lane changing effects of the vehicles on two adjacent lanes. It results from integrating the Taylor series expansion of the viscous continuum traffic flow model proposed by Ge (2006 Physics A 371 667) into the multi-lane model presented by Daganzo (1997Transpn. Res. B 31 83). Our proposed model may be used to describe non-anisotropic behaviour because of lane changing in multi-lane traffic. A linear stability analysis is given and the neutral stability condition is obtained. Also,issues related to lane changing,shock waves and rarefaction waves,local clustering and phase transition are investigated through a simulation experiment. The simulation results show that the proposed model is capable of explaining some particular traffic phenomena commonly observable in real world traffic flow.
Towards a Flow-based Internet Traffic Classification for Bandwidth Optimization
Directory of Open Access Journals (Sweden)
Abuagla Babiker Mohd
2009-05-01
Full Text Available Abstract The evolution of the Internet into a large complex service-based network has posed tremendous challenges for network monitoring and control in terms of how to collect the large amount of data in addition to the accurate classification of new emerging applications such as peer to peer, video streaming and online gaming. These applications consume bandwidth and affect the performance of the network especially in a limited bandwidth networks such as university campuses causing performance deterioration of mission critical applications. Some of these new emerging applications are designed to avoid detection by using dynamic port numbers (port hopping, port masquerading (use http port 80 and sometimes encrypted payload. Traditional identification methodologies such as port-based signature-based are not efficient for today’s traffic. In this work machine learning algorithms are used for the classification of traffic to their corresponding applications. Furthermore this paper uses our own customized made training data set collected from the campus, The effect on the amount of training data set has been considered before examining, the accuracy of various classification algorithms and selecting the best. Our findings show that random tree, IBI, IBK, random forest respectively provide the top 4 highest accuracy in classifying flow based network traffic to their corresponding application among thirty algorithms with accuracy not less than 99.33%.
Deriving average delay of traffic flow around intersections from vehicle trajectory data
Institute of Scientific and Technical Information of China (English)
Minyue ZHAO; Xiang LI
2013-01-01
Advances of positioning and wireless communication technologies make it possible to collect a large number of trajectory data of moving vehicles in a fast and convenient fashion.The data can be applied to various fields such as traffic study.In this paper,we attempt to derive average delay of traffic flow around intersections and verify the results with changes of time.The intersection zone is delineated first.Positioning points geographically located within this zone are selected,and then outliers are removed.Turn trips are extracted from selected trajectory data.Each trip,physically consisting of time-series positioning points,is identified with entry road segment and turning direction,i.e.target road segment.Turn trips are grouped into different categories according to their time attributes.Then,delay of each trip during a turn is calculated with its recorded speed.Delays of all trips in the same period of time are plotted to observe the change pattern of traffic conditions.Compared to conventional approaches,the proposed method can be applied to those intersections without fixed data collection devices such as loop detectors since a large number of trajectory data can always provide a more complete spatio-temporal picture of a road network.With respect to data availability,taxi trajectory data and an intersection in Shanghai are employed to test the proposed methodology.Results demonstrate its applicability.
An improved multi-value cellular automata model for heterogeneous bicycle traffic flow
Energy Technology Data Exchange (ETDEWEB)
Jin, Sheng [College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, 310058 China (China); Qu, Xiaobo [Griffith School of Engineering, Griffith University, Gold Coast, 4222 Australia (Australia); Xu, Cheng [Department of Transportation Management Engineering, Zhejiang Police College, Hangzhou, 310053 China (China); College of Transportation, Jilin University, Changchun, 130022 China (China); Ma, Dongfang, E-mail: mdf2004@zju.edu.cn [Ocean College, Zhejiang University, Hangzhou, 310058 China (China); Wang, Dianhai [College of Civil Engineering and Architecture, Zhejiang University, Hangzhou, 310058 China (China)
2015-10-16
This letter develops an improved multi-value cellular automata model for heterogeneous bicycle traffic flow taking the higher maximum speed of electric bicycles into consideration. The update rules of both regular and electric bicycles are improved, with maximum speeds of two and three cells per second respectively. Numerical simulation results for deterministic and stochastic cases are obtained. The fundamental diagrams and multiple states effects under different model parameters are analyzed and discussed. Field observations were made to calibrate the slowdown probabilities. The results imply that the improved extended Burgers cellular automata (IEBCA) model is more consistent with the field observations than previous models and greatly enhances the realism of the bicycle traffic model. - Highlights: • We proposed an improved multi-value CA model with higher maximum speed. • Update rules are introduced for heterogeneous bicycle traffic with maximum speed 2 and 3 cells/s. • Simulation results of the proposed model are consistent with field bicycle data. • Slowdown probabilities of both regular and electric bicycles are calibrated.
Self-organized Natural Roads for Predicting Traffic Flow: A Sensitivity Study
Jiang, Bin; Yin, Junjun
2008-01-01
In this paper, we extended road-based topological analysis into both nationwide and urban road networks, and concentrated on a sensitivity study with respect to the formation of self-organized natural roads based on Gestalt principle of good continuity. Both Annual Average Daily Traffic (AADT) and Global Positioning System (GPS) data were used to correlate with a series of ranking metrics including five centrality-based metrics and two PageRank metrics. It was found that there exists a tipping point from segment- to road-based network topology in terms of correlation between ranking metrics and their traffic. To our big surprise, (1) this correlation is significantly improved if a selfish rather than utopian strategy is adopted in forming the self-organized natural roads, and (2) point-based metrics assigned by summation into individual roads tend to have a much better correlation with traffic flow than line-based metrics. These counter-intuitive surprising findings constitute emergent properties of self-orga...
Modeling Mixed Bicycle Traffic Flow: A Comparative Study on the Cellular Automata Approach
Directory of Open Access Journals (Sweden)
Dan Zhou
2015-01-01
Full Text Available Simulation, as a powerful tool for evaluating transportation systems, has been widely used in transportation planning, management, and operations. Most of the simulation models are focused on motorized vehicles, and the modeling of nonmotorized vehicles is ignored. The cellular automata (CA model is a very important simulation approach and is widely used for motorized vehicle traffic. The Nagel-Schreckenberg (NS CA model and the multivalue CA (M-CA model are two categories of CA model that have been used in previous studies on bicycle traffic flow. This paper improves on these two CA models and also compares their characteristics. It introduces a two-lane NS CA model and M-CA model for both regular bicycles (RBs and electric bicycles (EBs. In the research for this paper, many cases, featuring different values for the slowing down probability, lane-changing probability, and proportion of EBs, were simulated, while the fundamental diagrams and capacities of the proposed models were analyzed and compared between the two models. Field data were collected for the evaluation of the two models. The results show that the M-CA model exhibits more stable performance than the two-lane NS model and provides results that are closer to real bicycle traffic.
How can macroscopic models reveal self-organization in traffic flow?
Cristiani, Emiliano; Tosin, Andrea
2012-01-01
In this paper we propose a new modeling technique for vehicular traffic flow, designed for capturing at a macroscopic level some effects, due to the microscopic granularity of the flow of cars, which would be lost with a purely continuous approach. The starting point is a multiscale method for pedestrian modeling, recently introduced in Cristiani et al., Multiscale Model. Simul., 2011, in which measure-theoretic tools are used to manage the microscopic and the macroscopic scales under a unique framework. In the resulting coupled model the two scales coexist and share information, in the sense that the same system is simultaneously described from both a discrete (microscopic) and a continuous (macroscopic) perspective. This way it is possible to perform numerical simulations in which the single trajectories and the average density of the moving agents affect each other. Such a method is here revisited in order to deal with multi-population traffic flow on networks. For illustrative purposes, we focus on the si...
Analysis of Phase Transition in Traffic Flow based on a New Model of Driving Decision
Peng, Yu; Shang, Hua-Yan; Lu, Hua-Pu
2011-07-01
Different driving decisions will cause different processes of phase transition in traffic flow. To reveal the inner mechanism, this paper built a new cellular automaton (CA) model, based on the driving decision (DD). In the DD model, a driver's decision is divided into three stages: decision-making, action, and result. The acceleration is taken as a decision variable and three core factors, i.e. distance between adjacent vehicles, their own velocity, and the preceding vehicle's velocity, are considered. Simulation results show that the DD model can simulate the synchronized flow effectively and describe the phase transition in traffic flow well. Further analyses illustrate that various density will cause the phase transition and the random probability will impact the process. Compared with the traditional NaSch model, the DD model considered the preceding vehicle's velocity, the deceleration limitation, and a safe distance, so it can depict closer to the driver preferences on pursuing safety, stability and fuel-saving and has strong theoretical innovation for future studies.
Analysis of Phase Transition in Traffic Flow based on a New Model of Driving Decision
Institute of Scientific and Technical Information of China (English)
PENG Yu; SHANG Hua-Yan; LU Hua-Pu
2011-01-01
Different driving decisions will cause different processes of phase transition in traffic flow. To reveal the inner mechanism, this paper built a new cellular automaton (CA) model, based on the driving decision (DD). In the DD model, a driver's decision is divided into three stages: decision-making, action, and result. The acceleration is taken as a decision variable and three core factors, i.e. distance between adjacent vehicles, their own velocity, and the preceding vehicle's velocity, are considered. Simulation results show that the DD model can simulate the synchronized flow effectively and describe the phase transition in traffic flow well. Further analyses illustrate that various density will cause the phase transition and the random probability will impact the process. Compared with the traditional NaSch model, the DD model considered the preceding vehicle's velocity, the deceleration limitation, and a safe distance, so it can depict closer to the driver preferences on pursuing safety, stability and fuel-saving and has strong theoretical innovation for future studies.
A new and efficient adaptive scheduling packets for the uplink traffic in WiMAX networks
Directory of Open Access Journals (Sweden)
Teixeira Marcio
2011-01-01
Full Text Available Abstract In this article, an adaptive scheduling packets algorithm for the uplink traffic in WiMAX networks is proposed. The proposed algorithm is designed to be completely dynamic, mainly in networks that use various modulation and coding schemes (MCSs. Using a cross-layer approach and the states of the uplink virtual queues in the base station, it was defined a new deadlines-based scheme, aiming at limiting the maximum delay to the real-time applications. Moreover, a method which interacts with the polling mechanisms of the base station was developed. This method controls the periodicity of sending unicast polling to the real-time and non-real-time service classes, in accordance with the quality of service requirements of the applications. The proposed algorithm was evaluated by means of modeling and simulation in environments where various MCSs were used and also in an environment where only one type of MCS was used. The simulations showed satisfactory results in both environments.
Mechanisms of jamming in the Nagel-Schreckenberg model for traffic flow
Bette, Henrik M.; Habel, Lars; Emig, Thorsten; Schreckenberg, Michael
2017-01-01
We study the Nagel-Schreckenberg cellular automata model for traffic flow by both simulations and analytical techniques. To better understand the nature of the jamming transition, we analyze the fraction of stopped cars P (v =0 ) as a function of the mean car density. We present a simple argument that yields an estimate for the free density where jamming occurs, and show satisfying agreement with simulation results. We demonstrate that the fraction of jammed cars P (v ∈{0 ,1 }) can be decomposed into the three factors (jamming rate, jam lifetime, and jam size) for which we derive, from random walk arguments, exponents that control their scaling close to the critical density.
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Ibsen, Lars Bo
2010-01-01
. In current research the authors utilized the Differential Transformation Method (DTM) for solving the nonlinear problem and compared the analytical results with those ones obtained by the 4th order Runge-Kutta Method (RK4) as a numerical method. Further illustration embedded in this paper shows the ability...... of DTM in solving nonlinear problems when a so accurate solution is required.......In this paper we aim to find an analytical solution for jamming transition in traffic flow. Generally the Jamming Transition Problem (JTP) can be modeled via Lorentz system. So, in this way, the governing differential equation achieved is modeled in the form of a nonlinear damped oscillator...
L^1 stability of conservation laws for a traffic flow model
Directory of Open Access Journals (Sweden)
Tong Li
2001-02-01
Full Text Available We establish the $L^1$ well-posedness theory for a system of nonlinear hyperbolic conservation laws with relaxation arising in traffic flows. In particular, we obtain the continuous dependence of the solution on its initial data in $L^1$ topology. We construct a functional for two solutions which is equivalent to the $L^1$ distance between the solutions. We prove that the functional decreases in time which yields the $L^1$ well-posedness of the Cauchy problem. We thus obtain the $L^1$-convergence to and the uniqueness of the zero relaxation limit.
Phase transitions in a new car-following traffic flow model
Institute of Scientific and Technical Information of China (English)
Li Li; Shi Peng-Fei
2005-01-01
In this paper, we investigate the performance of the well-known optimal velocity car-following model(the OVM) with numerical simulation in describing the acceleration process that is induced by the motion of a ldading car with a pre-specifide speed profile. Results show that this model is to some extent deficient in performing this process. Modification of the OVM to overcome the deficiency is demonstrated. The linear stability for the modified model is analysed. If the linear stability condition can not be satisfied, phase transitions occur on varying the initial homogeneous headway of the traffic flow.
Online Optimal Control of Connected Vehicles for Efficient Traffic Flow at Merging Roads
Energy Technology Data Exchange (ETDEWEB)
Rios-Torres, Jackeline [ORNL; Malikopoulos, Andreas [ORNL; Pisu, Pierluigi [Clemson University
2015-01-01
This paper addresses the problem of coordinating online connected vehicles at merging roads to achieve a smooth traffic flow without stop-and-go driving. We present a framework and a closed-form solution that optimize the acceleration profile of each vehicle in terms of fuel economy while avoiding collision with other vehicles at the merging zone. The proposed solution is validated through simulation and it is shown that coordination of connected vehicles can reduce significantly fuel consumption and travel time at merging roads.
Adaptive Routing Algorithm for Priority Flows in a Network
2012-06-14
Protocol 5 IPv4 Internet Protocol version 4 16 IPv6 Internet Protocol version 6 16 Mbps Megabits per second 37 MCF Multicommodity Flow 19 MCFP...new packet header that, it places over top of the existing information. For example, the ARAP would utilize the Traffic Class field for IPv6 type...Chacòn, K. Whitebread. "Intelligent mobile agents in military command and control", in proceedings of the Workshop on Agents in Industry, in Autonomous
Research on an Urban Traffic Control System Based on DGPS
Institute of Scientific and Technical Information of China (English)
张锦; 张姝慧; 曹继红
2002-01-01
The basic principles of GPS (Global Positioning System) and DGPS (Differential GPS) are described. The principle and structure of vehicle navigation systems, and its application to the urban traffic flow guidance are analyzed. Then, an area-coordinated adaptive control system based on DGPS and a traffic flow guidance information system based on DGPS are put forward, and their working principles and functions are researched. This is to provides a new way for the development of urban road traffic control systems.
Carrillo, Snaider; Harkin, Jim; McDaid, Liam; Pande, Sandeep; Cawley, Seamus; McGinley, Brian; Morgan, Fearghal
2012-09-01
The brain is highly efficient in how it processes information and tolerates faults. Arguably, the basic processing units are neurons and synapses that are interconnected in a complex pattern. Computer scientists and engineers aim to harness this efficiency and build artificial neural systems that can emulate the key information processing principles of the brain. However, existing approaches cannot provide the dense interconnect for the billions of neurons and synapses that are required. Recently a reconfigurable and biologically inspired paradigm based on network-on-chip (NoC) and spiking neural networks (SNNs) has been proposed as a new method of realising an efficient, robust computing platform. However, the use of the NoC as an interconnection fabric for large-scale SNNs demands a good trade-off between scalability, throughput, neuron/synapse ratio and power consumption. This paper presents a novel traffic-aware, adaptive NoC router, which forms part of a proposed embedded mixed-signal SNN architecture called EMBRACE (EMulating Biologically-inspiRed ArChitectures in hardwarE). The proposed adaptive NoC router provides the inter-neuron connectivity for EMBRACE, maintaining router communication and avoiding dropped router packets by adapting to router traffic congestion. Results are presented on throughput, power and area performance analysis of the adaptive router using a 90 nm CMOS technology which outperforms existing NoCs in this domain. The adaptive behaviour of the router is also verified on a Stratix II FPGA implementation of a 4 × 2 router array with real-time traffic congestion. The presented results demonstrate the feasibility of using the proposed adaptive NoC router within the EMBRACE architecture to realise large-scale SNNs on embedded hardware.
Shang, Qiang; Lin, Ciyun; Yang, Zhaosheng; Bing, Qichun; Zhou, Xiyang
2016-01-01
Short-term traffic flow prediction is one of the most important issues in the field of intelligent transport system (ITS). Because of the uncertainty and nonlinearity, short-term traffic flow prediction is a challenging task. In order to improve the accuracy of short-time traffic flow prediction, a hybrid model (SSA-KELM) is proposed based on singular spectrum analysis (SSA) and kernel extreme learning machine (KELM). SSA is used to filter out the noise of traffic flow time series. Then, the filtered traffic flow data is used to train KELM model, the optimal input form of the proposed model is determined by phase space reconstruction, and parameters of the model are optimized by gravitational search algorithm (GSA). Finally, case validation is carried out using the measured data of an expressway in Xiamen, China. And the SSA-KELM model is compared with several well-known prediction models, including support vector machine, extreme learning machine, and single KLEM model. The experimental results demonstrate that performance of the proposed model is superior to that of the comparison models. Apart from accuracy improvement, the proposed model is more robust.
Infeld, E.; Rowlands, G.; Skorupski, A. A.
2014-10-01
We find a further class of exact solutions to the Lighthill-Whitham- Richards-Payne (LWRP) traffic flow equations. As before, using two consecutive Lagrangian transformations, a linearization is achieved. Next, depending on the initial density, we either obtain exact formulae for the dependence of the car density and velocity on x,t, or else, failing that, the same result in a parametric representation. The calculation always involves two possible factorizations of a consistency condition. Both must be considered. In physical terms, the lineup usually separates into two offshoots at different velocities. Each velocity soon becomes uniform. This outcome in many ways resembles not only that of Rowlands et al (2013 J. Phys. A: Math. Theor. 46 365202 (part I)) but also the two-soliton solution to the Korteweg-de Vries equation. This paper can be read independently of part I. This explains unavoidable repetitions. Possible uses of both papers in checking numerical codes are indicated. Since LWRP, numerous more elaborate models, including multiple lanes, traffic jams, tollgates, etc, abound in the literature. However, we present an exact solution. These are few and far between, other than found by inverse scattering. The literature for various models, including ours, is given. The methods used here and in part I may be useful in solving other problems, such as shallow water flow.
Effect of randomization in the Biham-Middleton-Levine traffic flow model
Ding, Zhong-Jun; Jiang, Rui; Huang, Wei; Wang, Bing-Hong
2011-06-01
This paper studies the effect of randomization in the Biham-Middleton-Levine (BML) traffic flow model. It is found that the average velocity exhibits a first-order phase transition from moving phase to jamming phase under periodic boundary conditions. The intermediate stable phase identified in the original deterministic BML model disappears with the introduction of randomization. The average velocity in the moving phase and the critical car density decrease as the randomization probability increases. We have developed a mean-field theory which successfully predicts the average velocity in the moving phase. Under open boundary conditions, there are only two phases and the maximum current phase does not occur. The dependence of the average velocity, the density and the flow rate on the injection probability in the moving phase have also been obtained through the mean-field theory.
Nonlocal multi-scale traffic flow models: analysis beyond vector spaces
Directory of Open Access Journals (Sweden)
Peter E. Kloeden
2016-08-01
Full Text Available Abstract Realistic models of traffic flow are nonlinear and involve nonlocal effects in balance laws. Flow characteristics of different types of vehicles, such as cars and trucks, need to be described differently. Two alternatives are used here, $$L^p$$ L p -valued Lebesgue measurable density functions and signed Radon measures. The resulting solution spaces are metric spaces that do not have a linear structure, so the usual convenient methods of functional analysis are no longer applicable. Instead ideas from mutational analysis will be used, in particular the method of Euler compactness will be applied to establish the well-posedness of the nonlocal balance laws. This involves the concatenation of solutions of piecewise linear systems on successive time subintervals obtained by freezing the nonlinear nonlocal coefficients to their values at the start of each subinterval. Various compactness criteria lead to a convergent subsequence. Careful estimates of the linear systems are needed to implement this program.
基于交通预测的多态交通流信号控制%Multi-state Flow Signal Control Based on Traffic Prediction
Institute of Scientific and Technical Information of China (English)
丁恒; 张卫华; 郑小燕; 陈无畏; 李阳阳
2012-01-01
The current signal control methods are insufficient in adaptability to multi-state traffic flow intersection. In order to solve this problem, on the basis of short-term traffic flow prediction, signal timing optimization for multi-state flow intersection was studied by setting multi-functional entrance lanes, vehicle detectors, lane controllers and other hardware facilities. According to the prediction data of traffic volume in intersection and signal control delay estimation model, multi-function lane flow direction was selected with the minimum total operation delay as the optimization target. Green light length was optimized gradually based on maximum queue length in every phase and signal control was implemented. Based on wavelet analysis, steady and random part of short-term traffic flow was predicted with radial basis function (RBF) neural network and Markov chain respectively. The multi-state flow signal control method at the intersection with multifunctional lanes was simulated by software VISSIM. The results show that this method can decrease the traffic delay effectively and improve service level of intersection.%为解决现有信号控制方法对多态交通流交叉口适应性不足的问题,通过在交叉口设置多功能进口车道和车辆检测器、车道控制器等硬件设施,进行了短时交通流预测基础上的多态交通流条件下交叉口信号配时优化研究。根据交通量预测数据,建立信号控制延误估计模型,以交叉口总延误最小为优化目标选取多功能车道流向,根据每相位最大排队长度逐步优化绿灯时长并实施信号控制。短时交通预测以小波分析为基础,采用RBF神经网络及Markov链分别预测交通流的稳态与随机部分。使用VISSIM软件对设置多功能车道的交叉口多态流信号控制方法进行了交通仿真。分析结果表明：该方法可有效降低行车延误,提高交叉口服务水平。
Adaptability of the Logistics System in National Economic Mobilization Based on Blocking Flow Theory
Directory of Open Access Journals (Sweden)
Xiangyuan Jing
2014-01-01
Full Text Available In the process of national economic mobilization, the logistics system usually suffers from negative impact and/or threats of such emergency events as wars and accidents, which implies that adaptability of the logistics system directly determines realization of economic mobilization. And where the real-time rescue operation is concerned, heavy traffic congestion is likely to cause a great loss of or damage to human beings and their properties. To deal with this situation, this article constructs a blocking-resistance optimum model and an optimum restructuring model based on blocking flow theories, of which both are illustrated by numerical cases and compared in characteristics and application. The design of these two models is expected to eliminate or alleviate the congestion situation occurring in the logistics system, thus effectively enhancing its adaptability in the national economic mobilization process.
Tian, Junfang; Ma, Shoufeng; Zhu, Chenqiang; Jiang, Rui; Ding, YaoXian
2015-01-01
This paper proposes an improved cellular automaton traffic flow model based on the brake light model, which takes into account that the desired time gap of vehicles is remarkably larger than one second. Although the hypothetical steady state of vehicles in the deterministic limit corresponds to a unique relationship between speeds and gaps in the proposed model, the traffic states of vehicles dynamically span a two-dimensional region in the plane of speed versus gap, due to the various randomizations. It is shown that the model is able to well reproduce (i) the free flow, synchronized flow, jam as well as the transitions among the three phases; (ii) the evolution features of disturbances and the spatiotemporal patterns in a car-following platoon; (iii) the empirical time series of traffic speed obtained from NGSIM data. Therefore, we argue that a model can potentially reproduce the empirical and experimental features of traffic flow, provided that the traffic states are able to dynamically span a 2D speed-gap...
Using Microsimulation Feedback For Trip Adaptation For Realistic Traffic In Dallas
Nagel, Kai; Barrett, Christopher L.
This paper presents a day-to-day re-routing relaxation approach for traffic simulations. Starting from an initial planset for the routes, the route- based microsimulation is executed. The result of the microsimulation is fed into a re-router, which re-routes a certain percentage of all trips. This approach makes the traffic patterns in the microsimulation much more reasonable. Further, it is shown that the method described in this paper can lead to strong oscillations in the solutions.
Institute of Scientific and Technical Information of China (English)
Sheng Peng; Zhao Shu-Long; Wang Jun-Feng; Tang Peng; Gao Lin
2009-01-01
This paper proposes a new combined cellular automaton (CA) model considering the driver behavior of stochastic acceleration and delay with the velocity of the preceding vehicle and the gap between the successive vehicles based on the WWH model and the noise-first NaSch model.It introduces the delay probability varying with the gap,adds the anticipation headway and increases the acceleration with a certain probability.Through these simulations,not only can the metastable state and start-stop wave be obtained but also the synchronized flow which the wide moving jam results in.Moreover,the effect of stochastic acceleration and delay on traffic flow is discussed by analyzing the correlation of traffic data.This indicates that synchronized flow easily emerges in the critical area between free flow and synchronized flow when acceleration and delay are synchronized or their probability is close to 0.5.
A Network Traffic Control Enhancement Approach over Bluetooth Networks
DEFF Research Database (Denmark)
Son, L.T.; Schiøler, Henrik; Madsen, Ole Brun
2003-01-01
This paper analyzes network traffic control issues in Bluetooth data networks as convex optimization problem. We formulate the problem of maximizing of total network flows and minimizing the costs of flows. An adaptive distributed network traffic control scheme is proposed as an approximated...... solution of the stated optimization problem that satisfies quality of service requirements and topologically induced constraints in Bluetooth networks, such as link capacity and node resource limitations. The proposed scheme is decentralized and complies with frequent changes of topology as well...... as capacity limitations and flow requirements in the network. Simulation shows that the performance of Bluetooth networks could be improved by applying the adaptive distributed network traffic control scheme...
STUDY OF CAR TRAFFIC FLOW STRUCTURE ON ARRIVAL AND DEPARTURE AT THE MARSHALLING YARD X
Directory of Open Access Journals (Sweden)
G. I. Nesterenko
2016-02-01
Full Text Available Purpose. The paper is aimed to analyse the existing car traffic organization at the marshalling yard aimed to reduce downtime of cars. Methodology. The methods of mathematical statistics allowed building the histogram of car traffic flow distribution at the marshalling yard and assessment of their parameters. The key quantitative and qualitative indicators of the station operation were analyzed. In order to analyze the effect of rehandling volume on the rehandled transit car downtime elements at the station we plotted the dependence graph of the car downtime elements on the rehandling volume. The curve variation on the graph clearly shows the effect of rehandling volume on two downtime elements: during formation and in expectation of operations. Findings. The question of reducing the average downtime of all car categories at the station should be solved by reducing unproductive downtime was proved. The correct determination of the average time spent by a rehandled transit car at the station is essential, especially in the conditions of new system of economic incentives. But still there is no separate methodology for determining the car downtime, which would allow to objectively consider the equipment and operation technology and exclude the possibility for subjective decisions. Originality. One of the main kinds of unproductive downtime during the carriage of goods by rail is a downtime on the marshalling yards in expectation of technological operations because of the system congestion. Reduction of this indicator is possible due to rational use of the marshalling yard capacity provided the rational distribution and car – and train flows between the major marshalling yards of Ukrzaliznytsia. Practical value. The analysis of changes in downtime elements, depending on the rehandling volume allows not only to identify the car downtime reduction methods, but also to make a correct assessment of station staff work, as well as to adjust the rate of
Adaptive LES Methodology for Turbulent Flow Simulations
Energy Technology Data Exchange (ETDEWEB)
Oleg V. Vasilyev
2008-06-12
Although turbulent flows are common in the world around us, a solution to the fundamental equations that govern turbulence still eludes the scientific community. Turbulence has often been called one of the last unsolved problem in classical physics, yet it is clear that the need to accurately predict the effect of turbulent flows impacts virtually every field of science and engineering. As an example, a critical step in making modern computational tools useful in designing aircraft is to be able to accurately predict the lift, drag, and other aerodynamic characteristics in numerical simulations in a reasonable amount of time. Simulations that take months to years to complete are much less useful to the design cycle. Much work has been done toward this goal (Lee-Rausch et al. 2003, Jameson 2003) and as cost effective accurate tools for simulating turbulent flows evolve, we will all benefit from new scientific and engineering breakthroughs. The problem of simulating high Reynolds number (Re) turbulent flows of engineering and scientific interest would have been solved with the advent of Direct Numerical Simulation (DNS) techniques if unlimited computing power, memory, and time could be applied to each particular problem. Yet, given the current and near future computational resources that exist and a reasonable limit on the amount of time an engineer or scientist can wait for a result, the DNS technique will not be useful for more than 'unit' problems for the foreseeable future (Moin & Kim 1997, Jimenez & Moin 1991). The high computational cost for the DNS of three dimensional turbulent flows results from the fact that they have eddies of significant energy in a range of scales from the characteristic length scale of the flow all the way down to the Kolmogorov length scale. The actual cost of doing a three dimensional DNS scales as Re{sup 9/4} due to the large disparity in scales that need to be fully resolved. State-of-the-art DNS calculations of isotropic
A Sarsa(λ-Based Control Model for Real-Time Traffic Light Coordination
Directory of Open Access Journals (Sweden)
Xiaoke Zhou
2014-01-01
Full Text Available Traffic problems often occur due to the traffic demands by the outnumbered vehicles on road. Maximizing traffic flow and minimizing the average waiting time are the goals of intelligent traffic control. Each junction wants to get larger traffic flow. During the course, junctions form a policy of coordination as well as constraints for adjacent junctions to maximize their own interests. A good traffic signal timing policy is helpful to solve the problem. However, as there are so many factors that can affect the traffic control model, it is difficult to find the optimal solution. The disability of traffic light controllers to learn from past experiences caused them to be unable to adaptively fit dynamic changes of traffic flow. Considering dynamic characteristics of the actual traffic environment, reinforcement learning algorithm based traffic control approach can be applied to get optimal scheduling policy. The proposed Sarsa(λ-based real-time traffic control optimization model can maintain the traffic signal timing policy more effectively. The Sarsa(λ-based model gains traffic cost of the vehicle, which considers delay time, the number of waiting vehicles, and the integrated saturation from its experiences to learn and determine the optimal actions. The experiment results show an inspiring improvement in traffic control, indicating the proposed model is capable of facilitating real-time dynamic traffic control.
Using microsimulation feedback for trip adaptation for realistic traffic in Dallas
Nagel, K; Nagel, Kai; Barrett, Christopher L
1997-01-01
This paper presents a day-to-day re-routing relaxation approach for traffic simulations. Starting from an initial planset for the routes, the route-based microsimulation is executed. The result of the microsimulation is fed into a re-router, which re-routes a certain percentage of all trips. This approach makes the traffic patterns in the microsimulation much more reasonable. Further, it is shown that the method described in this paper can lead to strong oscillations in the solutions.
Derivation, calibration and verification of macroscopic model for urban traffic flow. Part 1
Kholodov, Yaroslav A; Kholodov, Aleksandr S; Vasiliev, Mikhail O; Kurzhanskiy, Alexander A
2016-01-01
In this paper we present a second-order hydrodynamic traffic model that generalizes the existing second-order models of Payne-Whithem, Zhang and Aw-Rascle. In the proposed model, we introduce the pressure equation describing the dependence of "traffic pressure" on traffic density. The pressure equation is constructed for each road segment from the fundamental diagram that is estimated using measurements from traffic detectors. We show that properties of any phenomenological model are fully defined by the pressure equation. We verify the proposed model through simulations of the Interstate 580 freeway segment in California, USA, with traffic measurements from the Performance Measurement System (PeMS).
Considerations for Stationary Ice Covered Flows in Adaptive Hydraulics (ADH)
2009-05-01
Flows in Adaptive Hydraulics (ADH) by Gary L. Brown, Gaurav Savant , Charlie Berger, and David S. Smith Report Documentation Page Form ApprovedOMB No...Road, Vicksburg, MS 39180 at 601-634-3628, e-mail: Gary.L.Brown@usace.army.mil, or Dr. Gaurav Savant , P.E., Coastal and Hydraulics Laboratory, U.S...L., G. Savant , C.; Berger, and D. S. Smith. 2009. Considerations for stationary ice covered flows in ADaptive Hydraulics (ADH) ERDC TN-SWWRP- 09-4
Ullah, Sana; Kwak, Kyung Sup
2012-06-01
Wireless Body Area Network (WBAN) consists of low-power, miniaturized, and autonomous wireless sensor nodes that enable physicians to remotely monitor vital signs of patients and provide real-time feedback with medical diagnosis and consultations. It is the most reliable and cheaper way to take care of patients suffering from chronic diseases such as asthma, diabetes and cardiovascular diseases. Some of the most important attributes of WBAN is low-power consumption and delay. This can be achieved by introducing flexible duty cycling techniques on the energy constraint sensor nodes. Stated otherwise, low duty cycle nodes should not receive frequent synchronization and control packets if they have no data to send/receive. In this paper, we introduce a Traffic-adaptive MAC protocol (TaMAC) by taking into account the traffic information of the sensor nodes. The protocol dynamically adjusts the duty cycle of the sensor nodes according to their traffic-patterns, thus solving the idle listening and overhearing problems. The traffic-patterns of all sensor nodes are organized and maintained by the coordinator. The TaMAC protocol is supported by a wakeup radio that is used to accommodate emergency and on-demand events in a reliable manner. The wakeup radio uses a separate control channel along with the data channel and therefore it has considerably low power consumption requirements. Analytical expressions are derived to analyze and compare the performance of the TaMAC protocol with the well-known beacon-enabled IEEE 802.15.4 MAC, WiseMAC, and SMAC protocols. The analytical derivations are further validated by simulation results. It is shown that the TaMAC protocol outperforms all other protocols in terms of power consumption and delay.
Bertsimas, Dimitris; Odoni, Amedeo
1997-01-01
This document presents a critical review of the principal existing optimization models that have been applied to Air Traffic Flow Management (TFM). Emphasis will be placed on two problems, the Generalized Tactical Flow Management Problem (GTFMP) and the Ground Holding Problem (GHP), as well as on some of their variations. To perform this task, we have carried out an extensive literature review that has covered more than 40 references, most of them very recent. Based on the review of this emerging field our objectives were to: (i) identify the best available models; (ii) describe typical contexts for applications of the models; (iii) provide illustrative model formulations; and (iv) identify the methodologies that can be used to solve the models. We shall begin our presentation below by providing a brief context for the models that we are reviewing. In Section 3 we shall offer a taxonomy and identify four classes of models for review. In Sections 4, 5, and 6 we shall then review, respectively, models for the Single-Airport Ground Holding Problem, the Generalized Tactical FM P and the Multi-Airport Ground Holding Problem (for the definition of these problems see Section 3 below). In each section, we identify the best available models and discuss briefly their computational performance and applications, if any, to date. Section 7 summarizes our conclusions about the state of the art.
Efficient Foreground Extraction Based on Optical Flow and SMED for Road Traffic Analysis
Directory of Open Access Journals (Sweden)
K SuganyaDevi
2015-05-01
Full Text Available Foreground detection is a key procedure in video analysis such as object detection and tracking. Several foreground detection techniques and edge detectors have been developed until now but the problem is, usually it is difficult to obtain an optimal foreground due to weather, light, shadow and clutter interference. Background subtract is a common method in foreground detection. In background subtract noise appears at fixed place, when it is used to deal with long image sequence there may be much accumulate error in the foreground. In OF (Optical Flow noise appears randomly and this covers long distance over long period of time. Optical flow cannot get rid of the light influences which result in background noises. To overcome this SMED (Separable Morphological Edge Detector is used. SMED has robustness to light changing and even slight movement in the video sequence. This paper proposes a new foreground detection approach called OF and SMED which is more accurate in foreground detection and elimination of noises is very high. This approach is useful for efficient crowd and traffic monitoring, user friendly, highly automatic intelligent, computationally efficient system.
An Extended Cellular Automaton Model for Train Traffic Flow on the Dedicated Passenger Lines
Directory of Open Access Journals (Sweden)
Wenbo Zhao
2014-01-01
Full Text Available As one of the key components for the railway transportation system, the Train Operation Diagram can be greatly influenced by many extrinsic and intrinsic factors. Therefore, the railway train flow has shown the strong nonlinear characteristics, which makes it quite difficult to take further relative studies. Fortunately, the cellular automaton model has its own advantages in solving nonlinear problems and traffic flow simulation. Considering the mixed features of multispeed running trains on the passenger dedicated lines, this paper presents a new train model under the moving block system with different types of trains running with the cellular automaton idea. By analyzing such key factors as the maintenance skylight, the proportion of the multispeed running trains, and the distance between adjacent stations and departure intervals, the corresponding running rules for the cellular automaton model are reestablished herewith. By means of this CA model, the program of train running system is designed to analyze the potential impact on railway carrying capacity by various factors; the model can also be implemented to simulate the actual train running process and to draw the train operation diagram by computers. Basically the theory can be applied to organize the train operation on the dedicated passenger lines.
A two-dimensional CA model for traffic flow with car origin and destination
In-nami, Junji; Toyoki, Hiroyasu
2007-05-01
Dynamic phase transitions in a two-dimensional traffic flow model defined on a decorated square-lattice are studied numerically. The square-lattice point and the decorated site denote intersections and roads, respectively. In the present model, a car has a finite deterministic path between the origin and the destination, which is assigned to the car from the beginning. In this new model, we found a new phase between the free-flow phase and the frozen-jam phase that is absent from previous models. The new model is characterized by the persistence of a macroscopic cluster. Furthermore, the behavior in this macroscopic cluster phase is classified into three regions characterized by the shape of the cluster. The boundary of the three regions is phenomenologically estimated. When the trip length is short and the car density is high, both ends of the belt-like cluster connect to each other through the periodic boundary with some probability. This type of cluster is classified topologically as a string on a two-dimensional torus.
Yamamoto, Toshiaki; Ueda, Tetsuro; Obana, Sadao
As one of the dynamic spectrum access technologies, “cognitive radio technology,” which aims to improve the spectrum efficiency, has been studied. In cognitive radio networks, each node recognizes radio conditions, and according to them, optimizes its wireless communication routes. Cognitive radio systems integrate the heterogeneous wireless systems not only by switching over them but also aggregating and utilizing them simultaneously. The adaptive control of switchover use and concurrent use of various wireless systems will offer a stable and flexible wireless communication. In this paper, we propose the adaptive traffic route control scheme that provides high quality of service (QoS) for cognitive radio technology, and examine the performance of the proposed scheme through the field trials and computer simulations. The results of field trials show that the adaptive route control according to the radio conditions improves the user IP throughput by more than 20% and reduce the one-way delay to less than 1/6 with the concurrent use of IEEE802.16 and IEEE802.11 wireless media. Moreover, the simulation results assuming hundreds of mobile terminals reveal that the number of users receiving the required QoS of voice over IP (VoIP) service and the total network throughput of FTP users increase by more than twice at the same time with the proposed algorithm. The proposed adaptive traffic route control scheme can enhance the performances of the cognitive radio technologies by providing the appropriate communication routes for various applications to satisfy their required QoS.
Fang, Ya-Ling; Shi, Zhong-Ke; Cao, Jin-Liang
2015-06-01
Based on the coupled map car-following model which was presented by Konishi et al. (1999), a modified coupled map car-following model is proposed. Specifically, the velocity difference between two successive vehicles is included in the model. The stability condition is given for the change of the speed of the preceding vehicle on the base of the control theory. We derive a condition under which the traffic jam never occurs in our model. Furthermore, in order to suppress traffic jams, we use static and dynamic version of decentralized delayed-feedback control for each vehicle, respectively, and provide a systematic procedure for designing the controller. In addition, the controller of each vehicle does not include any other vehicle information in real traffic flows.
Adaptive Multi-Lag for Synthetic Aperture Vector Flow Imaging
DEFF Research Database (Denmark)
Villagómez Hoyos, Carlos Armando; Stuart, Matthias Bo; Jensen, Jørgen Arendt
2014-01-01
The range of detectable velocities in ultrasound flow imaging is linked to the user selection of pulse repetiti on frequency. Whenever a region with large differences in velo city magnitude is visualized, a trade-off has to be made. This work suggests an adaptive spatio-temporaly independent, m...
Data adaptive estimation of transversal blood flow velocities
DEFF Research Database (Denmark)
Pirnia, E.; Jakobsson, A.; Gudmundson, E.
2014-01-01
, posing natural difficulties due to the complex behaviour of blood flow, and due to the natural orientation of most blood vessels. Recently, a transversal modulation scheme was introduced to induce also an oscillation along the transversal direction, thereby allowing for the measurement of also...... the transversal blood flow. In this paper, we propose a novel data-adaptive blood flow estimator exploiting this modulation scheme. Using realistic Field II simulations, the proposed estimator is shown to achieve a notable performance improvement as compared to current state-of-the-art techniques....
Solution adaptive grids applied to low Reynolds number flow
de With, G.; Holdø, A. E.; Huld, T. A.
2003-08-01
A numerical study has been undertaken to investigate the use of a solution adaptive grid for flow around a cylinder in the laminar flow regime. The main purpose of this work is twofold. The first aim is to investigate the suitability of a grid adaptation algorithm and the reduction in mesh size that can be obtained. Secondly, the uniform asymmetric flow structures are ideal to validate the mesh structures due to mesh refinement and consequently the selected refinement criteria. The refinement variable used in this work is a product of the rate of strain and the mesh cell size, and contains two variables Cm and Cstr which determine the order of each term. By altering the order of either one of these terms the refinement behaviour can be modified.
A Risk-Hedged Approach to Traffic Flow Management under Atmospheric Uncertainties Project
National Aeronautics and Space Administration — Volcanic ash and other atmospheric hazards impact air transportation by introducing uncertainty in the National Airspace System (NAS) capacity. Deterministic traffic...
Adaptive Delayed Acknowledgement Algorithm for MPEG-4 Traffic in UWB Networks
Institute of Scientific and Technical Information of China (English)
LIU Xin; DAI Qionghai; WU Qiufeng
2006-01-01
Although ultra-wideband transmission rates are very high in the physical layer, the bandwidth utili-zation efficiency is very low in the medium access control (MAC) layer. The bandwidth utilization efficiencycan be improved and the quality of service for delay-sensitive variable bit rate traffic such as high rate mo-tion picture experts group (MPEG)-4 traffic can be guaranteed by a simple and efficient algorithm that dy-namically sets the burst size of the delayed-acknowledgement (Dly-ACK) based on the IEEE 802.15.3 stan-dard. The burst size was adjusted in response to the wireless channel quality. Furthermore, the burst sizewas bounded by a maximum acknowledgement burst size setting and the remaining number of un-receivedblocks of a current supra-block. Simulation results show that the method achieves significant performanceenhancement in the job failure rate and throughput compared to immediate-acknowledgement (Imm-ACK)and other fixed burst size Dly-ACK schemes. This algorithm can also be applied in generalized time divisionmultiple access (TDMA) systems by using the block acknowledgement mechanism for delay sensitive traffic.
Routing protocol of wireless sensor networks for traffic flow statistics%无线传感器网络车流量统计的路由协议
Institute of Scientific and Technical Information of China (English)
任秀丽; 谭振江
2012-01-01
提出了一种应用于交通管理中心统计道路车流量的路由协议,以便更好地进行交通管理.根据无线传感器网络能量有限的特点和具体应用的需求,在路由表中添加了车辆在检测区域内的有效时间,动态控制了中间节点是否转发信息,避免了基站接收无用信息,减少了节点的能量消耗.提出了一种节点唤醒策略,有效地提高了车流量统计应用中对目标追踪的质量.仿真实验表明:与AODV协议和TSR协议相比,延长了网络生存周期.%Routing protocol for traffic flow statistics is proposed to adapt for traffic management. Because of limited energy of wireless sensor networks and requirement of practical application, effective time of the vehicles in the detection region is added in the routing table in order to dynamicly control whether the middle node retransmits the message and to avoid the base station receiving useless information and the energy consumption of node is reduced. A wake-up strategy of nodes is proposed to improve the quality of the target tracking for traffic flow statistic. The simulation results show that the protocol prolongs the network lifetime compared with AODV and TSR protocols.
Adaptive multiresolution modeling of groundwater flow in heterogeneous porous media
Malenica, Luka; Gotovac, Hrvoje; Srzic, Veljko; Andric, Ivo
2016-04-01
Proposed methodology was originally developed by our scientific team in Split who designed multiresolution approach for analyzing flow and transport processes in highly heterogeneous porous media. The main properties of the adaptive Fup multi-resolution approach are: 1) computational capabilities of Fup basis functions with compact support capable to resolve all spatial and temporal scales, 2) multi-resolution presentation of heterogeneity as well as all other input and output variables, 3) accurate, adaptive and efficient strategy and 4) semi-analytical properties which increase our understanding of usually complex flow and transport processes in porous media. The main computational idea behind this approach is to separately find the minimum number of basis functions and resolution levels necessary to describe each flow and transport variable with the desired accuracy on a particular adaptive grid. Therefore, each variable is separately analyzed, and the adaptive and multi-scale nature of the methodology enables not only computational efficiency and accuracy, but it also describes subsurface processes closely related to their understood physical interpretation. The methodology inherently supports a mesh-free procedure, avoiding the classical numerical integration, and yields continuous velocity and flux fields, which is vitally important for flow and transport simulations. In this paper, we will show recent improvements within the proposed methodology. Since "state of the art" multiresolution approach usually uses method of lines and only spatial adaptive procedure, temporal approximation was rarely considered as a multiscale. Therefore, novel adaptive implicit Fup integration scheme is developed, resolving all time scales within each global time step. It means that algorithm uses smaller time steps only in lines where solution changes are intensive. Application of Fup basis functions enables continuous time approximation, simple interpolation calculations across
Directory of Open Access Journals (Sweden)
Zhenyu Mei
2012-01-01
Full Text Available The ongoing controversy about in what condition should we set the curb parking has few definitive answers because comprehensive research in this area has been lacking. Our goal is to present a set of heuristic urban street speed functions under mixed traffic flow by taking into account impacts of curb parking. Two impacts have been defined to classify and quantify the phenomena of motor vehicles' speed dynamics in terms of curb parking. The first impact is called Space impact, which is caused by the curb parking types. The other one is the Time impact, which results from the driver maneuvering in or out of parking space. In this paper, based on the empirical data collected from six typical urban streets in Nanjing, China, two models have been proposed to describe these phenomena for one-way traffic and two-way traffic, respectively. An intensive experiment has been conducted in order to calibrate and validate these proposed models, by taking into account the complexity of the model parameters. We also provide guidelines in terms of how to cluster and calculate those models' parameters. Results from these models demonstrated promising performance of modeling motor vehicles' speed for mixed traffic flow under the influence of curb parking.
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Beijing, known for having the worst traffic in China, is brewing up a traffic plan with the harshest ever measures to ensure smooth traffic flow as the capital’s gridlock during rush hour and private car sales soar.
An Efficient Methodology for Calibrating Traffic Flow Models Based on Bisection Analysis
Directory of Open Access Journals (Sweden)
Enzo C. Jia
2014-01-01
Full Text Available As urban planning becomes more sophisticated, the accurate detection and counting of pedestrians and cyclists become more important. Accurate counts can be used to determine the need for additional pedestrian walkways and intersection reorganization, among other planning initiatives. In this project, a camera-based approach is implemented to create a real-time pedestrian and cyclist counting system which is regularly accurate to 85% and often achieves higher accuracy. The approach retasks a state-of-the-art traffic camera, the Autoscope Solo Terra, for pedestrian and bicyclist counting. Object detection regions are sized to identify multiple pedestrians moving in either direction on an urban sidewalk and bicyclists in an adjacent bicycle lane. Collected results are processed in real time, eliminating the need for video storage and postprocessing. In this paper, results are presented for a pedestrian walkway for pedestrian flow up to 108 persons/min and the limitations of the implemented system are enumerated. Both pedestrian and cyclist counting accuracy of over 90% is achieved.
Kerner, Boris S.
2016-09-01
We have revealed general physical conditions for the maximization of the network throughput at which free flow conditions are ensured, i.e., traffic breakdown cannot occur in the whole traffic or transportation network. A physical measure of the network - network capacity is introduced that characterizes general features of the network with respect to the maximization of the network throughput. The network capacity allows us also to make a general proof of the deterioration of traffic system occurring when dynamic traffic assignment is performed in a network based on the classical Wardrop' user equilibrium (UE) and system optimum (SO) equilibrium.
灰色系统的交通流量短期预测%Short tern traffic flow forecasting of grey system
Institute of Scientific and Technical Information of China (English)
王凤琴; 柯亨进
2015-01-01
To alleviate traffic congestion problem, a gray model for short-term traffic flow forecasting application established, the road traffic conditions knew in advance, and led to play a traffic guidance.%为了缓解交通拥堵问题，建立灰色模型对交通流量进行短期预测，从而提前知道道路的交通状况，最终起到交通诱导。
Iwasaki, Yoichiro; Kawata, Shinya; Nakamiya, Toshiyuki
2011-08-01
We propose an algorithm for detecting vehicle positions and their movements by using thermal images obtained through an infrared thermography camera. The infrared thermography camera offers high contrast images even in poor visibility conditions like snow and thick fog. The proposed algorithm specifies the area of moving vehicles based on the standard deviations of pixel values along the time direction of spatio-temporal images. It also specifies vehicle positions by applying the pattern recognition algorithm which uses Haar-like features per frame of the images. Moreover, to increase the accuracy of vehicle detection, correction procedures for misrecognition of vehicles are employed. The results of our experiments at three different temperatures show that the information about both vehicle positions and their movements can be obtained by combining those two kinds of detection, and the vehicle detection accuracy is 96.2%. Moreover, the proposed algorithm detects the vehicles robustly in the 222 continuous frames taken in poor visibility conditions like snow and thick fog. As an application of the algorithm, we also propose a method for estimating traffic flow conditions based on the results obtained by the algorithm. By using the method for estimating traffic flow conditions, automatic traffic flow monitoring can be achieved.
Delle Monache, M. L.; Goatin, P.
2014-12-01
We consider a strongly coupled PDE-ODE system that describes the influence of a slow and large vehicle on road traffic. The model consists of a scalar conservation law accounting for the main traffic evolution, while the trajectory of the slower vehicle is given by an ODE depending on the downstream traffic density. The moving constraint is expressed by an inequality on the flux, which models the bottleneck created in the road by the presence of the slower vehicle. We prove the existence of solutions to the Cauchy problem for initial data of bounded variation.
Li, Xiaoqin; Fang, Kangling; Peng, Guanghan
2017-02-01
In real traffic, aggressive driving behaviors often occurs by anticipating the front density of the next-nearest lattice site at next time step to adjust their acceleration in advance. Therefore, a new lattice model is put forward by considering the driver's aggressive effect (DAE). The linear stability condition is derived from the linear stability theory and the modified KdV equation near the critical point is obtained through nonlinear analysis with the consideration of aggressive driving behaviors, respectively. Both the analytical results and numerical simulation indicate that the driver's aggressive effect can increase the traffic stability. Thus driver's aggressive effect should be considered in traffic lattice model.
Directory of Open Access Journals (Sweden)
Virginia Puyana Romero
2016-09-01
Full Text Available High flows of road traffic noise in urban agglomerations can negatively affect the livability of squares and parks located at the neighborhood, district and city levels, therefore pushing anyone who wants to enjoy calmer, quieter areas to move to non-urban parks. Due to the distances between these areas, it is not possible to go as regularly as would be necessary to satisfy any needs. Even if cities are densely populated, the presence of a sea or riverfront offers the possibility of large restorative places, or at least with potential features for being the natural core of an urban nucleus after a renewal intervention. This study evaluates the soundscape of the Naples waterfront, presenting an overview of the most significant visual, acoustic and spatial factors related to the pedestrian areas, as well as areas open to road traffic and others where the road traffic is limited. The factors were chosen with feature selection methods and artificial neural networks. The results show how certain factors, such as the perimeter between the water and promenade, the visibility of the sea or the density of green areas, can affect the perception of the soundscape quality in the areas with road traffic. In the pedestrian areas, acoustic factors, such as loudness or the A-weighted sound level exceeded for 10% of the measurement duration (LA10, influence the perceived quality of the soundscape.
Traffic Adaptive Energy Efficient and Low Latency Medium Access Control for Wireless Sensor Networks
Yadav, Rajesh; Varma, Shirshu; Malaviya, N.
2008-05-01
Medium access control for wireless sensor networks has been a very active research area in the recent years. The traditional wireless medium access control protocol such as IEEE 802.11 is not suitable for the sensor network application because these are battery powered. The recharging of these sensor nodes is expensive and also not possible. The most of the literature in the medium access for the sensor network focuses on the energy efficiency. The proposed MAC protocol solves the energy inefficiency caused by idle listening, control packet overhead and overhearing taking nodes latency into consideration based on the network traffic. Simulation experiments have been performed to demonstrate the effectiveness of the proposed approach. The validation of the simulation results of the proposed MAC has been done by comparing it with the analytical model. This protocol has been simulated in Network Simulator ns-2.
Bicycle Conversion Factor Calibration at Two-Phase Intersections in Mixed Traffic Flows
Institute of Scientific and Technical Information of China (English)
WANG Dianhai; LIANG Chunyan; JING Chunguang; WANG Guohua
2007-01-01
Chinese traffic is typically composed of bicycles and motor vehicles on the same road. The efficiency of bicycle traffic in time and space at intersections was investigated for eight typical intersections in the cities of Tianjin, Shenyang, and Changchun, all in China, by means of video recording. Models were developed to calculate the through bicycle traffic and the left-turn bicycle traffic conversion factors in intersections where bicycles and motor vehicles share the same road. The results indicate that the through bicycle conversion factor is 0.28 and the left-turn bicycle conversion factor is 0.33. This conclusion differs from the current value used in China. More research on the conversion factor is necessary to evaluate the impact of intersections.
A multilevel adaptive projection method for unsteady incompressible flow
Howell, Louis H.
1993-11-01
There are two main requirements for practical simulation of unsteady flow at high Reynolds number: the algorithm must accurately propagate discontinuous flow fields without excessive artificial viscosity, and it must have some adaptive capability to concentrate computational effort where it is most needed. We satisfy the first of these requirements with a second-order Godunov method similar to those used for high-speed flows with shocks, and the second with a grid-based refinement scheme which avoids some of the drawbacks associated with unstructured meshes. These two features of our algorithm place certain constraints on the projection method used to enforce incompressibility. Velocities are cell-based, leading to a Laplacian stencil for the projection which decouples adjacent grid points. We discuss features of the multigrid and multilevel iteration schemes required for solution of the resulting decoupled problem. Variable-density flows require use of a modified projection operator--we have found a multigrid method for this modified projection that successfully handles density jumps of thousands to one. Numerical results are shown for the 2D adaptive and 3D variable-density algorithms.
Institute of Scientific and Technical Information of China (English)
何红弟; 董力耘; 戴世强
2006-01-01
Traffic flows controlled by traffic light strategies were investigated via a cellular automaton model with anticipation, which is suitable for describing urban traffic. Three kinds of strategies, i.e., synchronized, green-wave and random switching lights, were designed, simulated and compared with each other. It is shown that the green-wave strategy is only valid at lower density and there is not an effective way with the three strategies to improve the efficiency of traffic flow at high density.
Kerner, Boris S; Klenov, Sergey L; Schreckenberg, Michael
2014-05-01
Physical features of induced phase transitions in a metastable free flow at an on-ramp bottleneck in three-phase and two-phase cellular automaton (CA) traffic-flow models have been revealed. It turns out that at given flow rates at the bottleneck, to induce a moving jam (F → J transition) in the metastable free flow through the application of a time-limited on-ramp inflow impulse, in both two-phase and three-phase CA models the same critical amplitude of the impulse is required. If a smaller impulse than this critical one is applied, neither F → J transition nor other phase transitions can occur in the two-phase CA model. We have found that in contrast with the two-phase CA model, in the three-phase CA model, if the same smaller impulse is applied, then a phase transition from free flow to synchronized flow (F → S transition) can be induced at the bottleneck. This explains why rather than the F → J transition, in the three-phase theory traffic breakdown at a highway bottleneck is governed by an F → S transition, as observed in real measured traffic data. None of two-phase traffic-flow theories incorporates an F → S transition in a metastable free flow at the bottleneck that is the main feature of the three-phase theory. On the one hand, this shows the incommensurability of three-phase and two-phase traffic-flow theories. On the other hand, this clarifies why none of the two-phase traffic-flow theories can explain the set of fundamental empirical features of traffic breakdown at highway bottlenecks.
Research on Public Traffic Vehicles Dispatch Based on Improved Adaptive Genetic Algorithm
Institute of Scientific and Technical Information of China (English)
2010-01-01
<正>Bus dispatching has been studied,and also the bus dispatching model is set up.Then,Genetic Algorithm is adaptively improved in order to avoid premature problem and the slow convergence,and then the keeping optimal strategy is used to the Genetic Algorithm,so formed the Improved Adaptive Genetic Algorithm,namely IAGA. Finally,the IAGA is used to optimizing the bus dispatching model,and the results of the simulation indicate IAGA has the higher efficiency than simple GA and is one effective way to optimizing the bus dispatching.
Directory of Open Access Journals (Sweden)
Enrique Castillo
2015-01-01
Full Text Available A state-of-the-art review of flow observability, estimation, and prediction problems in traffic networks is performed. Since mathematical optimization provides a general framework for all of them, an integrated approach is used to perform the analysis of these problems and consider them as different optimization problems whose data, variables, constraints, and objective functions are the main elements that characterize the problems proposed by different authors. For example, counted, scanned or “a priori” data are the most common data sources; conservation laws, flow nonnegativity, link capacity, flow definition, observation, flow propagation, and specific model requirements form the most common constraints; and least squares, likelihood, possible relative error, mean absolute relative error, and so forth constitute the bases for the objective functions or metrics. The high number of possible combinations of these elements justifies the existence of a wide collection of methods for analyzing static and dynamic situations.
Estimation and Control of Networked Distributed Parameter Systems: Application to Traffic Flow
Canepa, Edward
2016-11-01
The management of large-scale transportation infrastructure is becoming a very complex task for the urban areas of this century which are covering bigger geographic spaces and facing the inclusion of connected and self-controlled vehicles. This new system paradigm can leverage many forms of sensing and interaction, including a high-scale mobile sensing approach. To obtain a high penetration sensing system on urban areas more practical and scalable platforms are needed, combined with estimation algorithms suitable to the computational capabilities of these platforms. The purpose of this work was to develop a transportation framework that is able to handle different kinds of sensing data (e.g., connected vehicles, loop detectors) and optimize the traffic state on a defined traffic network. The framework estimates the traffic on road networks modeled by a family of Lighthill-Whitham-Richards equations. Based on an equivalent formulation of the problem using a Hamilton-Jacobi equation and using a semi-analytic formula, I will show that the model constraints resulting from the Hamilton-Jacobi equation are linear, albeit with unknown integer variables. This general framework solve exactly a variety of problems arising in transportation networks: traffic estimation, traffic control (including robust control), cybersecurity and sensor fault detection, or privacy analysis of users in probe-based traffic monitoring systems. This framework is very flexible, fast, and yields exact results. The recent advances in sensors (GPS, inertial measurement units) and microprocessors enable the development low-cost dedicated devices for traffic sensing in cities, 5 which are highly scalable, providing a feasible solution to cover large urban areas. However, one of the main problems to address is the privacy of the users of the transportation system, the framework presented here is a viable option to guarantee the privacy of the users by design.
Institute of Scientific and Technical Information of China (English)
Qian Yong-Sheng; Shi Pei-Ji; Zeng Qiong; Ma Chang-Xi; Lin Fang; Sun Peng; Yin Xiao-Ting
2009-01-01
Based on the existing classical cellular automaton model of traffic flow,a cellular automaton traffic model with different-maximum-speed vehicles mixed on a single lane is proposed,in which public transit and harbour-shaped bus stops are taken into consideration. Parameters such as length of cellular automaton,operation speed and random slow mechanism are re-demarcated. A harbour-shaped bus stop is set up and the vehicle changing lane regulation is changed.Through computer simulation,the influence of occupation rate of public transit vehicles on mixed traffic flow and traffic capacity is analysed. The results show that a public transport system can ease urban traffic congestion hut creates new jams at the same time,and that the influence of occupation rate of public transit vehicles on traffic capacity is considerable. To develop urban traffic,attention should be paid to the occupation rate of public transit vehicles and traffic development in a haphazard way should be strictly avoided.
基于无线传感器网络的自适应交通灯控制系统%An Adaptive Traffic Light Control System Based on Wireless Sensor Networks
Institute of Scientific and Technical Information of China (English)
刘信新; 陈鲲
2011-01-01
By analyzing the existing traffic light control systems, an adaptive traffic light control system based on wireless sensor networks is proposed. The flow rate of vehicles is measured by using the wireless ultrasonic sensor nodes deployed on the road. The scheduling process of traffic lights is modeled and analyzed. An adaptive scheduling algorithm is presented, and simulation results show that this algorithm is able to reduce average waiting time of vehicles and improve traffic efficiency.%分析了现有信号灯控制系统的优缺点,提出了一种基于无线传感器网络的交通灯控制系统设计方案,利用敷设在路面上的携带超声波收发模块的传感器节点探测各方向车道上车流量,并根据车流量实时改变相应车道车辆放行时间,以提高道路利用率,减少拥堵现象.本系统可准确地获得车流量统计信息.对信号灯调度过程进行了建模分析,提出了自适应的调度算法,仿真实验结果表明,该算法能降低车辆平均等待时间,提高通行效率.
Modeling Traffic Flow and Management at Un-signalized, Signalized and Roundabout Road Intersections
Directory of Open Access Journals (Sweden)
R. Kakooza
2005-01-01
Full Text Available Traffic congestion continues to hinder economic and social development and also has a negative impact on the environment. A simple mathematical model is used to analyze the different types of road intersections in terms of their Performance in relation to managing traffic congestion and to establish the condition for stability of the road intersections after sufficiently longer periods of time (steady-state. In the analysis, single and double lane un-signalized, signalized and roundabout intersections are evaluated on the basis of their performance (expected number of vehicles and waiting time. Experimental scenarios are carefully designed to analyze the performance of the different types of intersections. It is noted that under light traffic, roundabout intersections perform better than un-signalized and signalized in terms of easing congestion. However under heavy traffic, signalized intersection perform better in terms of easing traffic congestion compared to un-signalized and roundabout intersections. It is further noted that for stability of a road intersection, the proportion of the time a road link stopping at an intersection is delayed should not exceed the utilization factor (the ratio of the arrival rate of vehicles to the product of number of service channels and service rate.
Directory of Open Access Journals (Sweden)
P. Swetha,
2014-06-01
Full Text Available Back pressure-based adaptive routing algorithms where each packet is routed along a possibly different pathhave been extensively studied in the literature. However, suchalgorithms typically result in poor delay performance and involvehigh implementation complexity. In this paper, we develop anew adaptive routing algorithm built upon the widely-studiedback-pressure algorithm. We decouple the routing and schedulingcomponents of the algorithm by designing a probabilistic routingtable which is used to route packets to per-destination queues.The scheduling decisions in the case of wireless networks aremade using counters called shadow queues. The results arealso extended to the case of networks which employ simpleforms of network coding. In that case, our algorithm provides alow-complexity solution to optimally exploit the routing-codingtrade-off.
Influence of geometric design characteristics on safety under heterogeneous traffic flow
Directory of Open Access Journals (Sweden)
Praveen Vayalamkuzhi
2016-12-01
Full Text Available This paper focuses on analysing the influence of geometric design characteristics on traffic safety using bi-directional data on a divided roadway operated under heterogeneous traffic conditions in India. The study was carried out on a four lane divided inter-city highway in plain and rolling terrain. Statistical modelling approach by Poisson regression and Negative binomial regression were used to assess the safety performance as occurrence of crashes are random events and to identify the influence of the geometric design variables on the crash frequency. Negative binomial regression model was found to be more suitable to identify the variables contributing to road crashes. The study enabled better understanding of the factors related to road geometrics that influence road crash frequency. The study also established that operating speed has a significant contribution to the total number of crashes. Negative binomial models are found to be appropriate to predict road crashes on divided roadways under heterogeneous traffic conditions.
Energy Technology Data Exchange (ETDEWEB)
Makigami, Y. (Ritsumeikan Univ., Kyoto (Japan). Faculty of Engineering); Toyota, (Japan Highway Public Corp., Tokyo (Japan)); Matsuo, T. (Hanshin Expressway Public Corp., Osaka (Japan))
1992-01-20
The report is aimed at giving an idea about design of the weaving section or traffic plan, which describes the outline and the results of a series of traffic survay and capacity analysis on weaving section on the Central Loop and its neighboring section of the Hanshin Expressway in 1985 to 1990 by making use of both areal photographs taken from a helicopter and video recordings and which makes an effort to clear which area does the traffic jam caused by the narrow road affect on and how does the mechanism show while making search the characteristics of the traffic flow in a weaving section. Using these traffic data, the applicability of HCM-85 Weaving Capacity Analysis Method to the Japanese expressway is evaluated. It also makes a touch to the problems and study about analysis method of weaving section. 11 refs., 21 figs., 3 tabs.
A control method applied to mixed traffic flow for the coupled-map car-following model
Cheng, Rong-Jun; Han, Xiang-Lin; Lo, Siu-Ming; Ge, Hong-Xia
2014-03-01
In light of previous work [Phys. Rev. E 60 4000 (1999)], a modified coupled-map car-following model is proposed by considering the headways of two successive vehicles in front of a considered vehicle described by the optimal velocity function. The non-jam conditions are given on the basis of control theory. Through simulation, we find that our model can exhibit a better effect as p = 0.65, which is a parameter in the optimal velocity function. The control scheme, which was proposed by Zhao and Gao, is introduced into the modified model and the feedback gain range is determined. In addition, a modified control method is applied to a mixed traffic system that consists of two types of vehicle. The range of gains is also obtained by theoretical analysis. Comparisons between our method and that of Zhao and Gao are carried out, and the corresponding numerical simulation results demonstrate that the temporal behavior of traffic flow obtained using our method is better than that proposed by Zhao and Gao in mixed traffic systems.
Characteristics of traffic flow at a non-signalized intersection in the framework of game theory
Fan, Hongqiang; Jia, Bin; Tian, Junfang; Yun, Lifen
2014-12-01
At a non-signalized intersection, some vehicles violate the traffic rules to pass the intersection as soon as possible. These behaviors may cause many traffic conflicts even traffic accidents. In this paper, a simulation model is proposed to research the effects of these behaviors at a non-signalized intersection. Vehicle’s movement is simulated by the cellular automaton (CA) model. The game theory is introduced for simulating the intersection dynamics. Two types of driver participate the game process: cooperator (C) and defector (D). The cooperator obey the traffic rules, but the defector does not. A transition process may occur when the cooperator is waiting before the intersection. The critical value of waiting time follows the Weibull distribution. One transition regime is found in the phase diagram. The simulation results illustrate the applicability of the proposed model and reveal a number of interesting insights into the intersection management, including that the existence of defectors is benefit for the capacity of intersection, but also reduce the safety of intersection.
Conservation laws with a non-local flow application to pedestrian traffic
Directory of Open Access Journals (Sweden)
Lécureux-Mercier Magali
2013-01-01
Full Text Available In this note, we introduce some models of pedestrian traffic and prove existence and uniqueness of solutions for these models. On présente ici différents modèles de trafic piéton et on prouve l’existence et l’unicité des solutions pour ces modèles.
Goal-oriented model adaptivity for viscous incompressible flows
van Opstal, T. M.
2015-04-04
© 2015, Springer-Verlag Berlin Heidelberg. In van Opstal et al. (Comput Mech 50:779–788, 2012) airbag inflation simulations were performed where the flow was approximated by Stokes flow. Inside the intricately folded initial geometry the Stokes assumption is argued to hold. This linearity assumption leads to a boundary-integral representation, the key to bypassing mesh generation and remeshing. It therefore enables very large displacements with near-contact. However, such a coarse assumption cannot hold throughout the domain, where it breaks down one needs to revert to the original model. The present work formalizes this idea. A model adaptive approach is proposed, in which the coarse model (a Stokes boundary-integral equation) is locally replaced by the original high-fidelity model (Navier–Stokes) based on a-posteriori estimates of the error in a quantity of interest. This adaptive modeling framework aims at taking away the burden and heuristics of manually partitioning the domain while providing new insight into the physics. We elucidate how challenges pertaining to model disparity can be addressed. Essentially, the solution in the interior of the coarse model domain is reconstructed as a post-processing step. We furthermore present a two-dimensional numerical experiments to show that the error estimator is reliable.
基于SVM短时交通流量预测%Short-term Traffic Flow Prediction Based on SVM
Institute of Scientific and Technical Information of China (English)
蒋晓峰; 许伦辉; 朱悦
2012-01-01
Traffic flow prediction is a very important area in intelligent transportation systems. Traditional prediction methods have a very wide range of applications in the traffic prediction. But traditional prediction methods does not work very well in short-term traffic flow prediction because of the complexity of the influencing factors. With the development of machine learning and data mining,traffic flow prediction with a combination of machine learning and data mining has become more and more important as a research area. In this paper,SVM (Support Vector Machine) is used to build a short-term traffic flow prediction model,and Genetic Algorithm (GA) is used to optimize the SVM penalty factor C and kernel parameter a as well. The results of different kernel functions of SVM are compared,including polynomial kernel and RBF kernel. RBF SVM plays better than polynomial SVM with less training time and higher accuracy and SVM is very suitable for short-term traffic flow prediction.%交通流量预测是智能交通系统中非常重要的研究领域,传统的预测方法在交通流量预测中有着非常广泛的应用.但是,在短时交通流量预测中,由于其影响因素错综复杂,传统的预测方法对于短时交通流量不能很好地进行预测.随着机器学习和数据挖掘各种理论的不断提出及完善,机器学习和数据挖掘与交通流量预测的结合是智能交通系统未来发展的一个重要方向.本文利用SVM (support vector machine)构建了短时交通流量预测模型,并利用遗传算法(genetic algorithm)对SVM的惩罚参数C和核参数σ进行优化,同时比较SVM中不同核函数,包括多项式核函数(polynomial kernel)和径向基核函数(RBF kernel)的预测效果.径向基SVM (RBF SVM)训练时间要比多项式SVM (polynomial SVM)短,预测准确率和精度也要比多项式SVM要好.从仿真结果上看,SVM非常适合应用于短时交通流量预测,能够取得很好的预测效果与精度.
Directory of Open Access Journals (Sweden)
Fatemeh. Dehghani
2016-08-01
Full Text Available Network on chip has emerged as a long-term and effective method in Multiprocessor System-on-Chip communications in order to overcome the bottleneck in bus based communication architectures. Efficiency and performance of network on chip is so dependent on the architecture and structure of the network. In this paper a new structure and architecture for adaptive traffic control in network on chip using Code Division Multiple Access technique is presented. To solve the problem of synchronous access to bus based interconnection the code division multiple access technique was applied. In the presented structure that is based upon mesh topology and simple routing method we attempted to increase the exchanged data bandwidth rate among different cores. Also an attempt has been made to increase the performance by isolating the target address transfer path from data transfer path. The main goal of this paper is presenting a new structure to improve energy consumption, area and maximum frequency in network on chip systems using information coding and decoding techniques. The presented structure is simulated using Xilinx ISE software and the results show effectiveness of this architecture.
A Traffic Adaptive iSLIP Scheduling Algorithm%一种流量自适应的iSLIP算法
Institute of Scientific and Technical Information of China (English)
王景存; 张晓彤; 谢馨艾; 刘兰军
2007-01-01
针对iSLIP(iterative round robin matching with slip)算法在处理突发业务时性能严重恶化的问题,在iSLIP算法的基础上提出了一种流量自适应的时隙问迭代算法TA-iSLIP(traffic adaptive iSLIP).该算法根据队列长度智能判断当前流量情况,采取不同的调度策略,充分利用已经匹配的资源,使系统的匹配开销尽可能减小.并给出了TA-iSLIP的算法描述和性能评价,与iSLIP算法、FIRM(fcfs in round-robin matching)算法进行了比较.仿真结果表明,TA-iSLIP在均匀和非均匀流量下都达到了较好的性能,在非均匀流量下的吞吐率达到97%以上.
Institute of Scientific and Technical Information of China (English)
LI LI
2010-01-01
@@ Beijing, known for having the worst traffic in China, is brewing up a traffic plan with the harshest ever measures to ensure smooth traffic flow as the capital's gridlock during rush hour and private car sales soar. On December 13, the Beijing Municipal Government started soliciting public opinions for a draft plan designed to relieve the city's traffic problems.
An adaptive solution domain algorithm for solving multiphase flow equations
Katyal, A. K.; Parker, J. C.
1992-01-01
An adaptive solution domain (ASD) finite-element model for simulating hydrocarbon spills has been developed that is computationally more efficient than conventional numerical methods. Coupled flow of water and oil with an air phase at constant pressure is considered. In the ASD formulation, the solution domain for water- and oil-flow equations is restricted by eliminating elements from the global matrix assembly which are not experiencing significant changes in fluid saturations or pressures. When any nodes of an element exhibit changes in fluid pressures more than a stipulated tolerance τ, or changes in fluid saturations greater than tolerance τ 2 during the current time step, it is labeled active and included in the computations for the next iteration. This formulation achieves computational efficiency by solving the flow equations for only the part of the domain where changes in fluid pressure or the saturations take place above stipulated tolerances. Examples involving infiltration and redistribution of oil in 1- and 2-D spatial domains are described to illustrate the application of the ASD method and the savings in the processor time achieved by this formulation. Savings in the computational effort up to 84% during infiltration and 63% during redistribution were achieved for the 2-D example problem.
Directory of Open Access Journals (Sweden)
Yoichiro Iwasaki
2015-01-01
Full Text Available To realize road traffic flow surveillance under various environments which contain poor visibility conditions, we have already proposed two vehicle detection methods using thermal images taken with an infrared thermal camera. The first method uses pattern recognition for the windshields and their surroundings to detect vehicles. However, the first method decreases the vehicle detection accuracy in winter season. To maintain high vehicle detection accuracy in all seasons, we developed the second method. The second method uses tires’ thermal energy reflection areas on a road as the detection targets. The second method did not achieve high detection accuracy for vehicles on left-hand and right-hand lanes except for two center-lanes. Therefore, we have developed a new method based on the second method to increase the vehicle detection accuracy. This paper proposes the new method and shows that the detection accuracy for vehicles on all lanes is 92.1%. Therefore, by combining the first method and the new method, high vehicle detection accuracies are maintained under various environments, and road traffic flow surveillance can be realized.
Time, speeds, flows and densities in static models of road traffic congestion and congestion pricing
Verhoef, E.T.
1998-01-01
This paper studies some of the properties and fundamentals of static models of road traffic congestion that have triggered much debate in the literature. The first part of the paper focuses in particular on the difficulties arising with the backward-bending cost curve in the context of 'continuous congestion'. Therelevance of the backward-bending segment of the cost curve for the static analysis of congestion is questioned by demonstrating that 'equilibria' on this segment produce upwards shi...
Postural adaptations to repeated optic flow stimulation in older adults.
O'Connor, Kathryn W; Loughlin, Patrick J; Redfern, Mark S; Sparto, Patrick J
2008-10-01
The purpose of this study is to understand the processes of adaptation (changes in within-trial postural responses) and habituation (reductions in between-trial postural responses) to visual cues in older and young adults. Of particular interest were responses to sudden increases in optic flow magnitude. The postural sway of 25 healthy young adults and 24 healthy older adults was measured while subjects viewed anterior-posterior 0.4 Hz sinusoidal optic flow for 45 s. Three trials for each of three conditions were performed: (1) constant 12 cm optic flow amplitude (24 cm peak-to-peak), (2) constant 4 cm amplitude (8 cm p-t-p), and (3) a transition in amplitude from 4 to 12 cm. The average power of head sway velocity (P(vel)) was calculated for consecutive 5s intervals during the trial to examine the changes in sway within and between trials. A mixed factor repeated measures ANOVA was performed to examine the effects of subject Group, Trial, and Interval on the P(vel). P(vel) was greater in older adults in all conditions (phabituation. P(vel) of the older adults decreased significantly between all 3 trials, but decreased only between Trials 1 and 2 in young adults. While the responses of the young adults to the transition in optic flow from 4 to 12 cm did not significantly change, older adults had an increase in P(vel) following the transition, ranging from 6.5 dB for the first trial to 3.4 dB for the third trial. These results show that older adults can habituate to repeated visual perturbation exposures; however, this habituation requires a greater number of exposures than young adults. This suggests aging impacts the ability to quickly modify the relative weighting of the sensory feedback for postural stabilization.
无灯控错位交叉口交通流模型研究%Traffic Flow Model for Staggered Intersection without Signal Lamp
Institute of Scientific and Technical Information of China (English)
刘小明; 郑淑晖
2012-01-01
错位交叉口交通特性研究对于制定合理有效的错位交叉口交通管控策略具有重要意义.针对无灯控错位交叉口交通流间的冲突过程分别建立了相应的元胞自动机行为规则,进而应用上述规则对不同参数设置下的交通流演化过程进行数值模拟,并分析和讨论了主路进口道交通流密度变化对不同路段交通流平均速度的影响.研究结果表明,错位交叉口主路上较小的车流密度也能导致主路进口道及两T型口中间路段发生交通堵塞,每个T型口主路进口道交通流量变化会对另一个T型口主路进口道交通流平均速度产生较大影响,此外,无灯控下的交通堵塞也会呈现周期性的排队-消散过程.上述方法及结果可为错位交叉口实施信号控制提供有意义的指导.%Traffic characteristics investigation of staggered intersection lays the foundation of scientific and reasonable traffic control strategies. This paper first proposes the cellular automaton rules on the basis of the traffic conflict process analysis. Then with these rules, the traffic flow evolution under different parameters is presented by numerical simulations. The relationship between the arterial road traffic flow density and the average speed is explored. It is revealed that low traffic density on the main road of staggered intersections may lead to traffic congestions on the approach of main road and the road between two T-type intersections, and the average speed of traffic flow on each T-type import of main road was affected by the traffic flow changes of the other T-type approaches. Moreover, the traffic congestion on intersection without signal lamp is presented as a periodically queuing-dissipates process. The above methods and results provide meaningful guidance for traffic management and control implementation of staggered intersections without signal lamp.
Adaptive discontinuous Galerkin methods for non-linear reactive flows
Uzunca, Murat
2016-01-01
The focus of this monograph is the development of space-time adaptive methods to solve the convection/reaction dominated non-stationary semi-linear advection diffusion reaction (ADR) equations with internal/boundary layers in an accurate and efficient way. After introducing the ADR equations and discontinuous Galerkin discretization, robust residual-based a posteriori error estimators in space and time are derived. The elliptic reconstruction technique is then utilized to derive the a posteriori error bounds for the fully discrete system and to obtain optimal orders of convergence. As coupled surface and subsurface flow over large space and time scales is described by (ADR) equation the methods described in this book are of high importance in many areas of Geosciences including oil and gas recovery, groundwater contamination and sustainable use of groundwater resources, storing greenhouse gases or radioactive waste in the subsurface.
Exact solution of a delay difference equation modeling traffic flow and their ultra-discrete limit
Matsuya, Keisuke; Kanai, Masahiro
2015-01-01
We consider a car-following model described by a delay difference equation and give its exact solutions that present propagation of a traffic jam. This model is a discrete-time version of the delayed optimal-velocity model; in the continuum limit, we recover the delay differential equation for this model and the exact solutions as well. We then work in the ultra-discrete limit, obtaining a delay cellular-automaton model, which successfully inherits the solutions. Also the dispersion relation ...
Nagapetyan, Tigran
2011-01-01
In this work we widespread statistical physics (chemical kinetic stochastic) approach to the investigation of macrosystems, arise in economic, sociology and traffic flow theory. The main line is a definition of equilibrium of macrosystem as most probable macrostate of invariant measure of Markov dynamic (corresponds to the macrosystem). We demonstrate new dynamical interpretations for the well known static model of correspondence matrix calculation. Based on this model we propose a best response dynamics for the Beckmann's traffic flow distribution model. We prove that this "natural" dynamic under quite general conditions converges to the Nash-Wardrop's equilibrium. After that we consider two interesting demonstration examples.
Tadaki, Shin-ichi; Kikuchi, Macoto; Nakayama, Akihiro; Shibata, Akihiro; Sugiyama, Yuki; Yukawa, Satoshi
2016-08-01
From a physics point of view, the emergence of a traffic jam is considered to be a dynamical phase transition. To verify this, we performed a series of circuit experiments. In previous work, Tadaki et al (2013 New J. Phys 15 103034), we confirmed the occurrence of this phase transition and estimated the critical density between free and jammed flows by analyzing the fundamental diagram. In this paper, we characterize and distinguish free and jammed flows, beyond the analyses of fundamental diagrams, according to the distribution and correlation of experimental speed data. We find that the speed in free flow does not correlate and its distribution has a narrow single peak at the average. The distribution of speed in jammed flow has two peaks or a single broad peak. The two peaks indicate the car speeds inside and outside of jam clusters. The broad single peak appears as a result of the appearance and disappearance of jam clusters. We also find that the formation of jam clusters induces a long correlation in speed. We can identify the size of jam clusters and the relative distance between coexisting jam clusters from this speed correlation.
Traffic forecaster for MPLS multimedia data streams
Ambrose, Barry; Lin, Freddie
2006-05-01
Contemporary high performance data networks carry a wide range of multimedia services (voice, video, audio, text, sensor data, etc.) that require an outstanding Quality of Service (QoS) to provide performance guarantees in priority delivery, latency, bandwidth utilization, load balancing, etc. With the advent of recent Multi-Protocol Label Switching (MPLS) network standards, the QoS has made significant progress in performance to provide these performance guarantees. Right now, attention has turned to the task of managing these QoS networks more efficiently through the handling of network traffic. We have investigated a novel Network Traffic Forecasting Assisted QoS Planner technology that will provide constantly updated forecasts of data traffic and server loads to any application that needs this information. Using source models of voice, video and data traffic based on empirical studies of TCP/IP data traffic carried out by Paxson and Floyd in the 1990's, our studies have shown that the system may provide up to 43% bandwidth savings for MPLS data streams, by predicting future traffic flows and reserving network resources to accommodate the predicted traffic. The system additionally provides a means to submit bandwidth reservation requests for those applications that need assured service guarantees for data delivery. The technology essentially increases the efficiency and effectiveness of multimedia information and communication network infrastructure that supports multiple or adaptive QoS levels for multimedia data networking and information system applications.
ANALYSIS OF TRAFFIC CONDITIONS IN URBAN THOROUGHFARES
Kovalenko, L.; Urdzik, S.
2006-01-01
Results of experimental investigations into descriptions of traffic flows in urban thoroughfares have been considered. Dependencies between traffic speed, density and intensity for various traffic conditions have been offered.
The theoretical analysis of the lattice hydrodynamic models for traffic flow theory
Ge, H. X.; Cheng, R. J.; Lei, L.
2010-07-01
The lattice hydrodynamic model is not only a simplified version of the macroscopic hydrodynamic model, but also connected with the microscopic car following model closely. The modified Korteweg-de Vries (mKdV) equation related to the density wave in a congested traffic region has been derived near the critical point since Nagatani first proposed it. But the Korteweg-de Vries (KdV) equation near the neutral stability line has not been studied, which has been investigated in detail for the car following model. We devote ourselves to obtaining the KdV equation from the original lattice hydrodynamic models and the KdV soliton solution to describe the traffic jam. Especially, we obtain the general soliton solution of the KdV equation and the mKdV equation. We review several lattice hydrodynamic models, which were proposed recently. We compare the modified models and carry out some analysis. Numerical simulations are conducted to demonstrate the nonlinear analysis results.
Directory of Open Access Journals (Sweden)
Toshiyuki Nakamiya
2013-06-01
Full Text Available We have already proposed a method for detecting vehicle positions and their movements (henceforth referred to as “our previous method” using thermal images taken with an infrared thermal camera. Our experiments have shown that our previous method detects vehicles robustly under four different environmental conditions which involve poor visibility conditions in snow and thick fog. Our previous method uses the windshield and its surroundings as the target of the Viola-Jones detector. Some experiments in winter show that the vehicle detection accuracy decreases because the temperatures of many windshields approximate those of the exterior of the windshields. In this paper, we propose a new vehicle detection method (henceforth referred to as “our new method”. Our new method detects vehicles based on tires’ thermal energy reflection. We have done experiments using three series of thermal images for which the vehicle detection accuracies of our previous method are low. Our new method detects 1,417 vehicles (92.8% out of 1,527 vehicles, and the number of false detection is 52 in total. Therefore, by combining our two methods, high vehicle detection accuracies are maintained under various environmental conditions. Finally, we apply the traffic information obtained by our two methods to traffic flow automatic monitoring, and show the effectiveness of our proposal.
Sun, Yi; Timofeyev, Ilya
2014-05-01
We employ an efficient list-based kinetic Monte Carlo (KMC) method to study traffic flow models on one-dimensional (1D) and two-dimensional (2D) lattices based on the exclusion principle and Arrhenius microscopic dynamics. This model implements stochastic rules for cars' movements based on the configuration of the traffic ahead of each car. In particular, we compare two different look-ahead rules: one is based on the distance from the car under consideration to the car in front of it, and the other one is based on the density of cars ahead. The 1D numerical results of these two rules suggest different coarse-grained macroscopic limits in the form of integro-differential Burgers equations. The 2D results of both rules exhibit a sharp phase transition from freely flowing to fully jammed, as a function of the initial density of cars. However, the look-ahead rule based on the density of the traffic produces more realistic results. The KMC simulations reported in this paper are compared with those from other well-known traffic flow models and the corresponding empirical results from real traffic.
Deterministic approach to microscopic three-phase traffic theory
Kerner, B S; Kerner, Boris S.; Klenov, Sergey L.
2005-01-01
A deterministic approach to three-phase traffic theory is presented. Two different deterministic microscopic traffic flow models are introduced. In an acceleration time delay model (ATD-model), different time delays in driver acceleration associated with driver behavior in various local driving situations are explicitly incorporated into the model. Vehicle acceleration depends on local traffic situation, i.e., whether a driver is within the free flow, or synchronized flow, or else wide moving jam traffic phase. In a speed adaptation model (SA-model), driver time delays are simulated as a model effect: Rather than driver acceleration, vehicle speed adaptation occurs with different time delays depending on one of the three traffic phases in which the vehicle is in. It is found that the ATD- and SA-models show spatiotemporal congested traffic patterns that are adequate with empirical results. It is shown that in accordance with empirical results in the ATD- and SA-models the onset of congestion in free flow at a...
Institute of Scientific and Technical Information of China (English)
熊伟晴; 燕晓波; 姜守旭; 李治军
2015-01-01
For the research and practice of modern intelligent transportation systems, short-term traffic flow prediction is an essential element. The main content of this paper is to establish a traffic prediction model for short-term traffic flow forecasting , using a rule-based fuzzy system, nonlinearly combine traffic flow forecasts resulting from an adaptive Kalman filter ( KF) and BP neural network model, which is referred as KBF model . Organic combination of traditional methods and artificial intelligence methods, on one hand, makes use of the powerful dynamic nonlinear mapping ability of artificial neural network, so as to improve the prediction accuracy;On the other hand, takes full advantages of the static linear sta-bility of the Kalman filter to solve the problem that the forecasts recognition rate is not satisfactory and the credibility is not high while using a BP neural network only. Verified by experiments, this model is useful for traffic flow forecasting with high accuracy and high reliability.%本文研究短时交通流预测。短时交通流预测是智能交通系统研究和实践的必要基础。本文提出和建立了一个短时交通流量预测模型，该模型利用一个基于规则的模糊系统，非线性地组合BP 神经网络模型和自适应卡尔曼滤波模型的交通流量预测结果，使得短时交通流量的预测结果更加准确可靠。该模型将传统方法和人工智能方法有机结合，一方面，利用人工神经网络强大的动态非线性映射能力，从而提高预测精度；另一方面，充分发挥卡尔曼滤波的静态线性稳定性，解决了单独使用BP神经网络进行预测时识别率不理想和可信度不高的问题。实验结果表明，本文提出的短时交通流预测模型具有较高的准确度和可靠度。
Traffic Flow of Interacting Self-Driven Particles: Rails and Trails, Vehicles and Vesicles
Chowdhury, Debashish
One common feature of a vehicle, an ant and a kinesin motor is that they all convert chemical energy, derived from fuel or food, into mechanical energy required for their forward movement; such objects have been modelled in recent years as self-driven particles. Cytoskeletal filaments, e.g., microtubules, form a rail network for intra-cellular transport of vesicular cargo by molecular motors like, for example, kinesins. Similarly, ants move along trails while vehicles move along lanes. Therefore, the traffic of vehicles and organisms as well as that of molecular motors can be modelled as systems of interacting self-driven particles; these are of current interest in non-equilibrium statistical mechanics. In this paper we point out the common features of these model systems and emphasize the crucial differences in their physical properties.
Simulation evaluation of TIMER, a time-based, terminal air traffic, flow-management concept
Credeur, Leonard; Capron, William R.
1989-01-01
A description of a time-based, extended terminal area ATC concept called Traffic Intelligence for the Management of Efficient Runway scheduling (TIMER) and the results of a fast-time evaluation are presented. The TIMER concept is intended to bridge the gap between today's ATC system and a future automated time-based ATC system. The TIMER concept integrates en route metering, fuel-efficient cruise and profile descents, terminal time-based sequencing and spacing together with computer-generated controller aids, to improve delivery precision for fuller use of runway capacity. Simulation results identify and show the effects and interactions of such key variables as horizon of control location, delivery time error at both the metering fix and runway threshold, aircraft separation requirements, delay discounting, wind, aircraft heading and speed errors, and knowledge of final approach speed.
高速公路安全与交通流特征参数关系%Relationship Between Traffic Flow and Safety on Freeway
Institute of Scientific and Technical Information of China (English)
钟连德; 孙小端
2013-01-01
With 3-year' s traffic flow data and crash data of a freeway in plain terrain in China, the relationship between traffic flow and safety was analyzed. Besides the amount of traffic volume influences the crash occurrence absolutely, truck percent, the speed difference between truck and car, and the ratio of traffic volume to capacity are the most three prominent parameters. The interactive impact also existed among the traffic flow parameters inside, so how and to what extent the single parameter impacted the road safety was changeable, and some functions made sense only when other parameters were confined in the specific conditions. The authors developed several kinds of mathematical relationships that described the combined effects of traffic flow characteristics on crash occurrences, which can enable engineers to identify and implement effective countermeasures to reduce the probability of crashes.%基于我国平原区1条典型高速公路3年的事故数据和交通流数据对两者之间的关系进行了研究.利用多变量多项式比率等方法建立了多个交通流参数和事故率之间的关系方程,并辅以三维曲面图加以直观反映.研究表明:大车比例、大小车平均速度差和饱和度是影响交通安全最为重要的3个交通流特征参数,多个交通流参数之间相互作用关系复杂,单个参数对交通安全的影响随着其他参数取值的变化而变化.
Kerner, Boris S
2010-01-01
We present results of numerical simulations of the effect of driver behavior on spatiotemporal congested traffic patterns that result from traffic breakdown at an on-ramp bottleneck. The simulations are made with the Kerner-Klenov stochastic traffic flow model in the framework of three-phase traffic theory. Different diagrams of congested patterns at the bottleneck associated with different driver behavioral characteristics are found and compared each other. An adaptive cruise control (ACC) in the framework of three-phase traffic theory introduced by the author (called a "driver alike ACC" (DA-ACC)) is discussed. The effect of DA-ACC-vehicles on traffic flow, in which without the DA-ACC-vehicles traffic congestion occurs at the bottleneck, is numerically studied. We show that DA-ACC-vehicles improve traffic flow considerably without any reduction in driving comfort. It is found that there is a critical percentage of DA-ACC-vehicles in traffic flow: If the percentage of the DA-ACC-vehicle exceeds the critical ...
Traffic-Adaptive, Flow-Specific Medium Access for Wireless Networks
2009-09-01
vol. 23, no. 12, pp. 1417–1433, Dec. 1975. [67] P. Karn, “MACA—A new channel access method for packet radio,” Proc. 9th ARRL Comput. Netw. Conf...and L. Meier, “Time synchronization and calibration in wireless sensor networks,” in Handbook of Sensor Networks: Algorithms and Architectures, I
Institute of Scientific and Technical Information of China (English)
臧利林; 朱文兴
2012-01-01
In order to reduce average delay time of passing vehicles and improve urban area traffic efficiency, considering actual geographical characteristics of intersections and sub-area traffic data, a control model for traffic signals at intersections was built based on optimizing sub-area traffic flows, and genetic algorithm was used to find out the optimal solution of the model. With traffic signals coordination of neighboring intersections considered, vehicle minimal delay time was chosen as the optimization object in the model. HCM2000 was adopted to calculate vehicle delay time and Robertson model was embedded in the optimization procedure, which ensured the proposed model to be feasible and effective. VC+ 3- 6. 0 software was applied to programm and calculate an optimal control plan for traffic signals at intersections. Finally, simulation by CORSIM was implemented to verifythe validity of the control plan. The results show that the proposed model can obtain better traffic efficiency than the coordination control method based on existing common cycle, and provides a new signal control idea at intersections for urban traffic.%为了减少车辆平均延误时间,提高城市区域交通通行效率,结合实际交叉口地理特征和区域交通流数据,建立了一种基于子区域交通流优化的交叉口信号控制模型,并应用遗传算法获得模型的最优解。在模型中,考虑相邻交叉口信号之间的协调,以车辆平均延误时间最小为优化目标,采用HCM2000延误计算方法,并在优化过程中嵌入Robertson车队离散模型,保证提出模型的可行性和有效性。在VC＋＋6.0中编写程序,获得交叉口信号最优控制方案,最后通过CORSIM仿真证明该控制方案的优劣。结果表明：与现有基于共同周期的协调控制方法相比,所提出的模型能够获得更优的交通效益,为区域交通信号控制提供了一种新的思路。
Simulation of High-Level Way Toll Systemunder the Condition of Mixed Traffic Flow
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
Parking-toll on main-line is one of toll models on high-level ways in our country at present. This paper analyzes the flow' s distributing function, queuing model, and vehicle passing time. Through computer simulation, the negative index relationships between carrying capacity and serving time, and the index relationships between the queuing delay and flow are gained under the condition of different serving time and different vehicle type composition. When the flow density is low, the vehicle type composing has less influence on system serving level. Contrarily, also. Disposing toll station by roadway where flow density is high, we can save transection areas of toll station, reduce system queuing delay time, and enhance carrying capacity of toll station.
Muir, A P; Biek, R; Thomas, R; Mable, B K
2014-02-01
Both environmental and genetic influences can result in phenotypic variation. Quantifying the relative contributions of local adaptation and phenotypic plasticity to phenotypes is key to understanding the effect of environmental variation on populations. Identifying the selective pressures that drive divergence is an important, but often lacking, next step. High gene flow between high- and low-altitude common frog (Rana temporaria) breeding sites has previously been demonstrated in Scotland. The aim of this study was to assess whether local adaptation occurs in the face of high gene flow and to identify potential environmental selection pressures that drive adaptation. Phenotypic variation in larval traits was quantified in R. temporaria from paired high- and low-altitude sites using three common temperature treatments. Local adaptation was assessed using Q(ST)-F(ST) analyses, and quantitative phenotypic divergence was related to environmental parameters using Mantel tests. Although evidence of local adaptation was found for all traits measured, only variation in larval period and growth rate was consistent with adaptation to altitude. Moreover, this was only evident in the three mountains with the highest high-altitude sites. This variation was correlated with mean summer and winter temperatures, suggesting that temperature parameters are potentially strong selective pressures maintaining local adaptation, despite high gene flow.
A Modified Cellular Automaton Model for Traffic Flow%一种改进的交通流元胞自动机模型
Institute of Scientific and Technical Information of China (English)
葛红霞; 董力耘; 雷丽; 戴世强
2004-01-01
A modified cellular automaton model for traffic flow was proposed.A novel concept about the changeable security gap was introduced and a parameter related to the variable security gap was determined.The fundamental diagram obtained by simulation shows that the maximum flow more approaches to the observed data than that of the NaSch model,indicating that the presented model is more reasonable and realistic.
Analysis of Multi-Flight Common Routes for Traffic Flow Management
Sheth, Kapil; Clymer, Alexis; Morando, Alex; Shih, Fu-Tai
2016-01-01
This paper presents an approach for creating common weather avoidance reroutes for multiple flights and the associated benefits analysis, which is an extension of the single flight advisories generated using the Dynamic Weather Routes (DWR) concept. These multiple flight advisories are implemented in the National Airspace System (NAS) Constraint Evaluation and Notification Tool (NASCENT), a nation-wide simulation environment to generate time- and fuel-saving alternate routes for flights during severe weather events. These single flight advisories are clustered together in the same Center by considering parameters such as a common return capture fix. The clustering helps propose routes called, Multi-Flight Common Routes (MFCR), that avoid weather and other airspace constraints, and save time and fuel. It is expected that these routes would also provide lower workload for traffic managers and controllers since a common route is found for several flights, and presumably the route clearances would be easier and faster. This study was based on 30-days in 2014 and 2015 each, which had most delays attributed to convective weather. The results indicate that many opportunities exist where individual flight routes can be clustered to fly along a common route to save a significant amount of time and fuel, and potentially reducing the amount of coordination needed.
A method of variable speed limit control for traffic flow on freeway mainline%高速公路主线可变限速控制方法
Institute of Scientific and Technical Information of China (English)
马明辉; 杨庆芳; 梁士栋
2015-01-01
The traffic state would become congested at the bottleneck region during peak period, which increase travel time, and decrease efficiency. From time-space traffic characteristics on freeway mainline, macroscopic traffic flow model METANET is modified to describe the traffic flow with VSL control. Furthermore, based on the modified traffic flow models, establish the VSL models at bottleneck region, with the objective of improving traffic efficiency and decreasing travel time. As part of the VSL control algorithm, the proposed VSL control model is implemented at VISSIM simulation platform, the results reveal that the given VSL values according to real time traffic flow conditions can control the vehicles arriving effectively. Therefore, the implement of VSL control can improve traffic efficiency and decrease travel time effectively.%为了解决高流量状态下高速公路主线瓶颈区域交通流运行态势恶劣,导致车辆行程时间增加、道路通行效率降低等问题,从高速公路交通流运行时-空特性角度出发,对宏观交通模型METANET改进,使其能够描述可变限速控制条件下道路交通流运行状态,并以改进模型为基础,提高通行效率和缩短行程时间为目标,构建高速公路主线交通优化控制模型. 实验结果表明:高速公路主线可变限速控制方法能够根据道路交通流量的变化对安全限速值动态设置,实现对危险区车辆到达率的动态控制. 实施高速公路主线可变限速控制方法可有效提高道路通行效率,缩短车辆行程时间.
Decentralized Traffic Management Strategies for Sensor-Enabled Cars
Wang, Ziyuan; Ramamohanarao, Kotagiri
2009-01-01
Traffic Congestions and accidents are major concerns in today's transportation systems. This thesis investigates how to optimize traffic flow on highways, in particular for merging situations such as intersections where a ramp leads onto the highway. In our work, cars are equipped with sensors that can detect distance to neighboring cars, and communicate their velocity and acceleration readings with one another. Sensor-enabled cars can locally exchange sensed information about the traffic and adapt their behavior much earlier than regular cars. We propose proactive algorithms for merging different streams of sensor-enabled cars into a single stream. A proactive merging algorithm decouples the decision point from the actual merging point. Sensor-enabled cars allow us to decide where and when a car merges before it arrives at the actual merging point. This leads to a significant improvement in traffic flow as velocities can be adjusted appropriately. We compare proactive merging algorithms against the conventio...
ADAPTIVE FINITE ELEMENT METHOD FOR HIGH-SPEED FLOW-STRUCTURE INTERACTION
Institute of Scientific and Technical Information of China (English)
Wiroj LIMTRAKARN; Pramote DECHAUMPHAI
2004-01-01
An adaptive finite element method for high-speed flow-structure interaction is presented. The cell-centered finite element method is combined with an adaptive meshing technique to solve the Navier-Stokes equations for high-speed compressible flow behavior. The energy equation and the quasi-static structural equations for aerodynamically heated structures are solved by applying the Galerkin finite element method. The finite element formulation and computational procedure are described. Interactions between the high-speed flow, structural heat transfer, and deformation are studied by two applications of Mach 10 flow over an inclined plate, and Mach 4 flow in a channel.
Qiu, Shanwen
2013-09-01
In this article, we propose a new exact and grid-free numerical scheme for computing solutions associated with an hybrid traffic flow model based on the Lighthill-Whitham-Richards (LWR) partial differential equation, for a class of fundamental diagrams. In this hybrid flow model, the vehicles satisfy the LWR equation whenever possible, and have a constant acceleration otherwise. We first propose a mathematical definition of the solution as a minimization problem. We use this formulation to build a grid-free solution method for this model based on the minimization of component function. We then derive these component functions analytically for triangular fundamental diagrams, which are commonly used to model traffic flow. We also show that the proposed computational method can handle fixed or moving bottlenecks. A toolbox implementation of the resulting algorithm is briefly discussed, and posted at https://dl.dropbox.com/u/1318701/Toolbox.zip. © 2013 Elsevier Ltd.
Ding, Zhong-Jun; Jiang, Rui; Gao, Zi-You; Wang, Bing-Hong; Long, Jiancheng
2013-08-01
The effect of overpasses in the Biham-Middleton-Levine traffic flow model with random and parallel update rules has been studied. An overpass is a site that can be occupied simultaneously by an eastbound car and a northbound one. Under periodic boundary conditions, both self-organized and random patterns are observed in the free-flowing phase of the parallel update model, while only the random pattern is observed in the random update model. We have developed mean-field analysis for the moving phase of the random update model, which agrees with the simulation results well. An intermediate phase is observed in which some cars could pass through the jamming cluster due to the existence of free paths in the random update model. Two intermediate states are observed in the parallel update model, which have been ignored in previous studies. The intermediate phases in which the jamming skeleton is only oriented along the diagonal line in both models have been analyzed, with the analyses agreeing well with the simulation results. With the increase of overpass ratio, the jamming phase and the intermediate phases disappear in succession for both models. Under open boundary conditions, the system exhibits only two phases when the ratio of overpasses is below a threshold in the random update model. When the ratio of the overpass is close to 1, three phases could be observed, similar to the totally asymmetric simple exclusion process model. The dependence of the average velocity, the density, and the flow rate on the injection probability in the moving phase has also been obtained through mean-field analysis. The results of the parallel model under open boundary conditions are similar to that of the random update model.
An Optimal Flow Control Algorithm for Real-time Traffic over the Internet
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
According to the Wide Area Network model and queue dynamics in the router, the authors formulate the Internet flow control as a constrained convex programming problem, where the objective is to maximize the total utility and minimize transmission delay and delay jitter of all sources over their transmission rates. Based on this formulation, flow control can be solved by means of a gradient projection algorithm with properly rate iterations. The main difficulty facing the realization of the iteration algorithm is the distributed computation of the congestion measure. Fortunately, Explicit Congestion Notification (ECN) is likely to be used to improving the performance of TCP in the near future. By using ECN, it is possible to realize the iteration algorithm in IP networks. The algorithm is divided into two parts, algorithms in the router and the source. The main advantage of the scheme is its fast convergence ability and robustness, but small queue length fluctuation is unavoidable when the number of users increases.
考虑交通障碍的双车道扩展交通流模型%Extend Two-lane Traffic Flow Model with a Blockage
Institute of Scientific and Technical Information of China (English)
李建锋; 赵靖
2012-01-01
借助智能交通系统(ITS),把扩展的车辆跟驰模型应用于双车道,建立根据确定规则进行换道的扩展交通流跟驰模型.通过改变发车车头间距,在开放边界条件下左车道有交通事故发生时,重现实际交通中的交通流现象.数值模拟发现:双车道交通流模型能够有效地抑制交通流阻塞,提高交通流量.%The extended car-following model is applied into two-lane system based on intelligent transportation system application (ITS). Then, an extended model of two-lane traffic in which vehicles change the lane by a deterministic rule is presented. The typical traffic induced by a car accident on the left lane under the open boundary is investigated. The simulation results suggest that the two-lane traffic model can suppress the traffic jam and enhance the traffic flow effectively.
Multivalued fundamental diagrams of traffic flow in the kinetic Fokker-Planck limit
Visconti, Giuseppe; Puppo, Gabriella; Tosin, Andrea
2016-01-01
Starting from interaction rules based on two levels of stochasticity we study the influence of the microscopic dynamics on the macroscopic properties of vehicular flow. In particular, we study the qualitative structure of the resulting flux-density and speed-density diagrams for different choices of the desired speeds. We are able to recover multivalued diagrams as a result of the existence of a one-parameter family of stationary distributions, whose expression is analytically found by means of a Fokker-Planck approximation of the initial Boltzmann-type model.
车流量检测雷达系统信号处理研究%TRAFFIC FLOW MEASUREMENT RADAR SYSTEM SIGNAL PROCESSING RESEARCH
Institute of Scientific and Technical Information of China (English)
李秦君; 党宏社
2011-01-01
Designs one kind the traffic flow measurement radar system which as an input source of intelligent transport system, based on DSP technology to achieve an integrated signal processing, while using the feature which radar wave intermediate frequency signal contains information about how far from the object to radar, applies the related algorithm to carry on the spectral analysis to the intermediate frequency signal, to obtained access to the traffic lane information and the traffic flow statistics. Designed to achieve signal processing, traffic statistics and serial communication software system.%设计一种作为智能交通系统输入信息来源的车流量检测雷达系统,采用基于DSP的技术实现信号的综合处理,利用雷达波中频信号中包含了物体距离雷达有多远的信息这一特性,应用相关算法对中频信号进行频谱分析,获得车道信息并进行车流量统计.设计了实现系统信号处理、车流量统计及串口通信的软件系统.
Temporal-Spatial Analysis of Traffic Congestion Based on Modified CTM
Directory of Open Access Journals (Sweden)
Chenglong Chu
2015-01-01
Full Text Available A modified cell transmission model (CTM is proposed to depict the temporal-spatial evolution of traffic congestion on urban freeways. Specifically, drivers’ adaptive behaviors and the corresponding influence on traffic flows are emphasized. Two piecewise linear regression models are proposed to describe the relationship of flow and density (occupancy. Several types of cellular connections are designed to depict urban rapid roads with on/off-ramps and junctions. Based on the data collected on freeway of Queen Elizabeth, Ontario, Canada, we show that the new model provides a relatively higher accuracy of temporal-spatial evolution of traffic congestions.
Planning and managing rural recreational traffic flows: why the future can’t be more like the past
Jaarsma, C.F.; Vries, de J.R.; Beunen, R.
2009-01-01
The increasing popularity of rural tourism can cause traffic related problems at certain areas. Traffic congestion and parking problems are likely to occur as the infrastructure at these countryside destinations is seldom capable of dealing with the growing number of cars. Values which make the site
Anomaly detection for network traffic flow%网络流量异常检测
Institute of Scientific and Technical Information of China (English)
单蓉胜; 李建华; 王明政
2004-01-01
提出了一种新颖的网络洪流攻击的异常检测机制.这种检测机制的无状态维护、低计算代价的特性保证了自身具有抗洪流攻击的能力.本文以检测SYN洪流攻击为实例详细阐述了异常检测机制.这个机制应用EWMA方法检测网络流的突变, 并运用对称性分析方法检测网络流的异常活动.测试结果表明本文所提出的检测机制具有很好的检测洪流攻击的准确度, 并具有低延时特性.%This paper presents a novel mechanism for detecting flooding-attacks. The simplicity of the mechanism lies in its statelessness and low computation overhead, which makes the detection mechanism itself immune to flooding-attacks. In this paper, SYN-flooding, as an instance of flooding-attack, is used to illustrate the anomaly detection mechanism. The mechanism applies an exponentially weighted moving average (EWMA) method to detect the abrupt net flow and applies a symmetry analysis method to detect the anomaly activity of the network flow. Experiment shows that the mechanism has high detection accuracy and low detection latency.
Mirkin, Boris; Haddad, Jack; Shtessel, Yuri
2016-09-01
Asymptotical sliding mode-model reference adaptive control design for a class of systems with parametric uncertainty, unknown nonlinear perturbation and external disturbance, and with known input and state delays is proposed. To overcome the difficulty to directly predict the plant state under uncertainties, a control design is based on a developed decomposition procedure, where a 'generalised error' in conjunction with auxiliary linear dynamic blocks with adjustable gains is introduced and the sliding variable is formed on the basis of this error. The effect of such a decomposition is to pull the input delay out of first step of the design procedure. As a result, similarly to the classical Smith predictor, the adaptive control architecture based only on the lumped-delays, i.e. without conventional in such cases difficult-implemented distributed-delay blocks. Two new adaptive control schemes are proposed. A linearisation-based control design is constructed for feedback control of an urban traffic region model with uncertain dynamics. Simulation results demonstrate the effectiveness of the developed adaptive control method.
Adaptive management of river flows in Europe: A transferable framework for implementation
Summers, M. F.; Holman, I. P.; Grabowski, R. C.
2015-12-01
The evidence base for defining flow regimes to support healthy river ecosystems is weak, as there are few studies which quantify the ecological impact associated with different degrees of hydrological alteration. As a result, river flow standards used to manage water abstraction are largely based on expert judgement. Planned adaptive management studies on multiple rivers under the European Water Framework Directive represent an opportunity to learn about ecological flow requirements and improve the quantitative evidence base. However, identifying clear ecological responses to flow alteration can be a significant challenge, because of the complexity of river systems and the other factors which may confound the response. This paper describes the Adaptive River Management (ARM) framework, a flexible framework for implementing adaptive management of river flows that is transferable to other regions of the world. Application of the framework will ensure that the effectiveness of implemented management actions is appraised and that transferable quantitative data are collected that can be used in other geographical regions.
Parallel Mesh Adaptive Techniques for Complex Flow Simulation: Geometry Conservation
Directory of Open Access Journals (Sweden)
Angelo Casagrande
2012-01-01
Full Text Available Dynamic mesh adaptation on unstructured grids, by localised refinement and derefinement, is a very efficient tool for enhancing solution accuracy and optimising computational time. One of the major drawbacks, however, resides in the projection of the new nodes created, during the refinement process, onto the boundary surfaces. This can be addressed by the introduction of a library capable of handling geometric properties given by a CAD (computer-aided design description. This is of particular interest also to enhance the adaptation module when the mesh is being smoothed, and hence moved, to then reproject it onto the surface of the exact geometry.
Mixed Traffic Flow Capacity of More Major Lanes Unsignalized Intersection%主路多车道无信号交叉口混合交通流的通行能力
Institute of Scientific and Technical Information of China (English)
田新现
2008-01-01
Highway capacity is defined as maximum volume of traffic flow through the particular highway section under given traffic conditions,road conditions and so on.Highway construction and management is judged by capacity standard.The reasonable scale and time of highway construction,rational network structure and optimal management mode of highway network can be determined by analyzing the fitness between capacity and traffic volume.All over the world,highway capacity is studied to different extent in different country. Based on the gap acceptance theory,the mixed traffic flow composed of two representative vehicle types heavy and light vehicles is analyzed with probability theory.Capacity model of the minor mixed traffic flows crossing m major lanes,on which the traffic flows fix in with M3 distributed headway,on the unsignalized intersection is set up,and it is an extension of minor lane capacity theory for one vehicle-type and one major-lane traffic flow.
Wu, J J; Sun, H J; Gao, Z Y
2008-09-01
Detrended fluctuation analysis (DFA) is a useful tool to measure the long-range power-law correlations in 1f noise. In this paper, we investigate the power-law dynamics behavior of the density fluctuation time series generated by the famous Kerner-Klenov-Wolf cellular automata model in road traffic. Then the complexities of spatiotemporal, average speed, and the average density have been analyzed in detail. By introducing the DFA method, our main observation is that the free flow and wide moving jam phases correspond to the long-range anticorrelations. On the contrary, at the synchronized flow phase, the long-range correlated property is observed.
Rethinking Traffic Management: Design of Optimizable Networks
2008-06-01
traffic traverses each path in a network. On the Internet today, end hosts run congestion control to adapt sending rates, routers route traffic on...congestion control to adapt sending rates, routers route traffic on shortest paths based on link weights, and operators tune link weights to direct traffic...Chaintreau and Christophe Diot for giving me the opportunity to intern at Thomson Research Labs in Paris. Thanks to all the interns there for v making it
Poyneer, Lisa; van Dam, Marcos; Véran, Jean-Pierre
2009-04-01
We use closed-loop deformable mirror telemetry from Altair and Keck adaptive optics (AO) to determine whether atmospheric turbulence follows the frozen flow hypothesis. Using telemetry from AO systems, our algorithms (based on the predictive Fourier control framework) detect frozen flow >94% of the time. Usually one to three layers are detected. Between 20% and 40% of the total controllable phase power is due to frozen flow. Velocity vector RMS variability is less than 0.5 m/s (per axis) on 10-s intervals, indicating that the atmosphere is stable enough for predictive control to measure and adapt to prevailing atmospheric conditions before they change.
A New Traffic Flow Prediction Algorithm for Satellite Communication Network%一种新的卫星通信网流量预测算法*
Institute of Scientific and Technical Information of China (English)
秦红祥; 杨飞
2013-01-01
在通信网络的设计中，使用基于流量预测的网络规划已成为LTE发展的必然趋势。与地面网络不同，卫星网络由于受资源受限和拓扑时变的不利影响，其流量预测算法必须能兼顾精度和效率，这令传统的地面网络预测方法已不再适用。为了解决以上问题，提出了一种新的基于小波回声状态网络的流量预测算法，该算法通过小波多尺度分解的信号处理方法屏蔽了网络流量的噪声，而后结合了无反馈的回声状态网络联合进行预测。仿真证明，新算法相比传统算法能大幅提升网络流量的预测精度和运行效率，为卫星网络的流量规划提供了强有力的决策支持。%In the design of a communication network,it has become an inevitable trend with LET development to use traffic flow prediction method for network planning. Due to suffer from the constrained resource and change-able topology,the traffic flow prediction algorithm of the satellite networks which is different from terrestrial net-works,should fully take into account the accuracy and efficiency,so the traditional prediction methods for ter-restrial networks are no longer fit for application. In order to resolve this problem,a new traffic flow prediction algorithm based on wavelet and echo state networks is proposed in this paper. The new algorithm uses the signal processing method based on multi-scale decomposition of wavelet to shield the noise of the network traffic,and it combines with the non-feedback echo state network to predict. The simulation results show that the new algorithm can greatly improve the prediction accuracy and running efficiency of network traffic compared with traditional al-gorithms,so it provides a more scientific decision support for satellite communication network traffic planning.
Ge, H X; Dai, S Q; Dong, L Y; Xue, Y
2004-12-01
An extended car following model is proposed by incorporating an intelligent transportation system in traffic. The stability condition of this model is obtained by using the linear stability theory. The results show that anticipating the behavior of more vehicles ahead leads to the stabilization of traffic systems. The modified Korteweg-de Vries equation (the mKdV equation, for short) near the critical point is derived by applying the reductive perturbation method. The traffic jam could be thus described by the kink-antikink soliton solution for the mKdV equation. From the simulation of space-time evolution of the vehicle headway, it is shown that the traffic jam is suppressed efficiently with taking into account the information about the motion of more vehicles in front, and the analytical result is consonant with the simulation one.
2014-01-01
Both environmental and genetic influences can result in phenotypic variation. Quantifying the relative contributions of local adaptation and phenotypic plasticity to phenotypes is key to understanding the effect of environmental variation on populations. Identifying the selective pressures that drive divergence is an important, but often lacking, next step. High gene flow between high- and low-altitude common frog (Rana temporaria) breeding sites has previously been demonstrated in Scotland. ...
Adaptive Computations for Partial Differential Equations Governing Advective Fluid Flows
1990-12-27
metry, Journal of Electroanalytical Chemistry 282 (1990), 1-26. 16. H.K. Dahle, M.S. Espedal, R.E. Ewing, and 0. Saevareid, Characteristic adap- tive sub... Electroanalytical Chemistry , (to appear). 36. E.L. Isaacson, D. Marchesin, B.J. Plohr, and J.B. Temple, Multiphase flow mod- els with singular Riemann problems
Adaptive Multiscale Finite Element Method for Subsurface Flow Simulation
Van Esch, J.M.
2010-01-01
Natural geological formations generally show multiscale structural and functional heterogeneity evolving over many orders of magnitude in space and time. In subsurface hydrological simulations the geological model focuses on the structural hierarchy of physical sub units and the flow model addresses
Tsuji, Takuya; Yokomine, Takehiko; Shimizu, Akihiko
2002-11-01
We have been engaged in the development of multi-scale adaptive simulation technique for incompressible turbulent flow. This is designed as that important scale components in the flow field are detected automatically by lifting wavelet and solved selectively. In conventional incompressible scheme, it is very common to solve Poisson equation of pressure to meet the divergence free constraints of incompressible flow. It may be not impossible to solve the Poisson eq. in the adaptive way, but this is very troublesome because it requires generation of control volume at each time step. We gave an eye on weakly compressible model proposed by Bao(2001). This model was derived from zero Mach limit asymptotic analysis of compressible Navier-Stokes eq. and does not need to solve the Poisson eq. at all. But it is relatively new and it requires demonstration study before the combination with the adaptation by wavelet. In present study, 2-D and 3-D Backstep flow were selected as test problems and applicability to turbulent flow is verified in detail. Besides, combination of adaptation by wavelet with weakly compressible model towards the adaptive turbulence simulation is discussed.
Traffic Games: Modeling Freeway Traffic with Game Theory.
Cortés-Berrueco, Luis E; Gershenson, Carlos; Stephens, Christopher R
2016-01-01
We apply game theory to a vehicular traffic model to study the effect of driver strategies on traffic flow. The resulting model inherits the realistic dynamics achieved by a two-lane traffic model and aims to incorporate phenomena caused by driver-driver interactions. To achieve this goal, a game-theoretic description of driver interaction was developed. This game-theoretic formalization allows one to model different lane-changing behaviors and to keep track of mobility performance. We simulate the evolution of cooperation, traffic flow, and mobility performance for different modeled behaviors. The analysis of these results indicates a mobility optimization process achieved by drivers' interactions.
Traffic Games: Modeling Freeway Traffic with Game Theory
Cortés-Berrueco, Luis E.; Gershenson, Carlos; Stephens, Christopher R.
2016-01-01
We apply game theory to a vehicular traffic model to study the effect of driver strategies on traffic flow. The resulting model inherits the realistic dynamics achieved by a two-lane traffic model and aims to incorporate phenomena caused by driver-driver interactions. To achieve this goal, a game-theoretic description of driver interaction was developed. This game-theoretic formalization allows one to model different lane-changing behaviors and to keep track of mobility performance. We simulate the evolution of cooperation, traffic flow, and mobility performance for different modeled behaviors. The analysis of these results indicates a mobility optimization process achieved by drivers’ interactions. PMID:27855176
LSSVM Network Flow Prediction Based on the Self-adaptive Genetic Algorithm Optimization
Directory of Open Access Journals (Sweden)
Liao Wenjing
2013-02-01
Full Text Available In order to change the insufficiency of traditional network flow prediction and improve its accuracy, the paper proposed a kind of network flow prediction method based on the self-adaptive genetic least square support vector machine optimization. Through analyzing the individual parameter of the LS-SVM principle and self-adaptive remains algorithm, the network flow prediction model structure of GA-LSSVM, and the genetic model global operation parameters, this paper would conduct a performance test to the network flow simulation experiment. The simulation result showed that: compared with the traditional forecasting methods, the accuracy of its network flow prediction was higher than the traditional forecasting methods by using the least square support vector machine genetic optimization.
DISCONTINUITY-CAPTURING FINITE ELEMENT COMPUTATION OF UNSTEADY FLOW WITH ADAPTIVE UNSTRUCTURED MESH
Institute of Scientific and Technical Information of China (English)
DONG Genjin; LU Xiyun; ZHUANG Lixian
2004-01-01
A discontinuity-capturing scheme of finite element method (FEM) is proposed. The unstructured-grid technique combined with a new type of adaptive mesh approach is developed for both compressible and incompressible unsteady flows, which exhibits the capability of capturing the shock waves and/or thin shear layers accurately in an unsteady viscous flow at high Reynolds number.In particular, a new testing variable, i.e., the disturbed kinetic energy E, is suggested and used in the adaptive mesh computation, which is universally applicable to the capturing of both shock waves and shear layers in the inviscid flow and viscous flow at high Reynolds number. Based on several calculated examples, this approach has been proved to be effective and efficient for the calculations of compressible and incompressible flows.
Wavelet-based Adaptive Techniques Applied to Turbulent Hypersonic Scramjet Intake Flows
Frauholz, Sarah; Reinartz, Birgit U; Müller, Siegfried; Behr, Marek
2013-01-01
The simulation of hypersonic flows is computationally demanding due to large gradients of the flow variables caused by strong shock waves and thick boundary or shear layers. The resolution of those gradients imposes the use of extremely small cells in the respective regions. Taking turbulence into account intensives the variation in scales even more. Furthermore, hypersonic flows have been shown to be extremely grid sensitive. For the simulation of three-dimensional configurations of engineering applications, this results in a huge amount of cells and prohibitive computational time. Therefore, modern adaptive techniques can provide a gain with respect to computational costs and accuracy, allowing the generation of locally highly resolved flow regions where they are needed and retaining an otherwise smooth distribution. An h-adaptive technique based on wavelets is employed for the solution of hypersonic flows. The compressible Reynolds averaged Navier-Stokes equations are solved using a differential Reynolds s...
Adapted MR velocimetry of slow liquid flow in porous media
Huang, Li; Mikolajczyk, Gerd; Küstermann, Ekkehard; Wilhelm, Michaela; Odenbach, Stefan; Dreher, Wolfgang
2017-03-01
MR velocimetry of liquid flow in opaque porous filters may play an important role in better understanding the mechanisms of deep bed filtration. With this knowledge, the efficiency of separating the suspended solid particles from the vertically flowing liquid can be improved, and thus a wide range of industrial applications such as wastewater treatment and desalination can be optimized. However, MR velocimetry is challenging for such studies due to the low velocities, the severe B0 inhomogeneity in porous structures, and the demand for high spatial resolution and an appropriate total measurement time during which the particle deposition will change velocities only marginally. In this work, a modified RARE-based MR velocimetry method is proposed to address these issues for velocity mapping on a deep bed filtration cell. A dedicated RF coil with a high filling factor is constructed considering the limited space available for the vertical cell in a horizontal MR magnet. Several means are applied to optimize the phase contrast RARE MRI pulse sequence for accurately measuring the phase contrast in a long echo train, even in the case of a low B1 homogeneity. Two means are of particular importance. One uses data acquired with zero flow to correct the phase contrast offsets from gradient imperfections, and the other combines the phase contrast from signals of both odd and even echoes. Results obtained on a 7T preclinical MR scanner indicate that the low velocities in the heterogeneous system can be correctly quantified with high spatial resolution and an adequate total measurement time, enabling future studies on flow during the filtration process.
Institute of Scientific and Technical Information of China (English)
杨慧; 成卫; 肖海承; 潘云伟; 张东明
2011-01-01
针对中小城市临时交通管制措施下出现的交通拥堵状况,应用微观交通仿真软件TransModeler建立拥堵区域路网模型.运用动态交通组织手段来实现拥堵区域交通总量控制,均衡路网交通压力.以曲靖市中心城区拥堵区域动态交通组织优化为实例,通过仿真结果对方案实施前后的各拥堵路段的交通流运行状况进行评价,证明了流量调控方法对缓解拥堵区域交通状况具有一定的科学实效性.%For the traffic jams under the temporary traffic-control measures in small and medium-sized city, microscopic traffic simulation software TransModeler is applied for establishing regional network under the traffic congestion. Dynamic model of traffic organization means is used to realize total amount control of regional traffic congestion, and balance traffic pressure of network. And dynamic optimization of traffic congestion of the downtown area in Qujing city is took for example, it is through simulation results of optimizing organization before and after to evaluate traffic flow of each of road traffic congestion. It proves that flow adjustment methods can ease the regional traffic congestion and it has certain scientific effectiveness.
Automatic and efficient driving strategies while approaching a traffic light
Treiber, Martin
2014-01-01
Vehicle-infrastructure communication opens up new ways to improve traffic flow efficiency at signalized intersections. In this study, we assume that equipped vehicles can obtain information about switching times of relevant traffic lights in advance. This information is used to improve traffic flow by the strategies 'early braking', 'anticipative start', and 'flying start'. The strategies can be implemented in driver-information mode, or in automatic mode by an Adaptive Cruise Controller (ACC). Quality criteria include cycle-averaged capacity, driving comfort, fuel consumption, travel time, and the number of stops. By means of simulation, we investigate the isolated strategies and the complex interactions between the strategies and between equipped and non-equipped vehicles. As universal approach to assess equipment level effects we propose relative performance indexes and found, at a maximum speed of 50 km/h, improvements of about 15% for the number of stops and about 4% for the other criteria. All figures d...
Green Wave Traffic Optimization - A Survey
DEFF Research Database (Denmark)
Warberg, Andreas; Larsen, Jesper; Jørgensen, Rene Munk
The objective of this survey is to cover the research in the area of adaptive traffic control with emphasis on the applied optimization methods. The problem of optimizing traffic signals can be viewed in various ways, depending on political, economic and ecological goals. The survey highlights some......-based, approach, which is shown to be more suitable for adaptive traffic control. To support this claim three adaptive systems, which use alternatives to the classical optimization procedures, are described in detail....
Traffic Monitoring without single Car Detection from optical airborne Images
Zeller, Klaus; Hinz, Stefan; Rosenbaum, Dominik; Leitloff, Jens; Reinartz, Peter
2009-01-01
This article describes several methods for traffic monitoring from airborne optical remote sensing data. These methods classify the traffic into free flowing traffic, traffic congestion and traffic jam. Furthermore a method is explained, which provides information about the average speed of dense traffic on a defined part of the road. All methods gather the information directly from image features, without the use of single vehicle detection. The classification of the traffic is done by st...
Directory of Open Access Journals (Sweden)
Anesa Maolod Omar Al-Najeh
2012-07-01
Full Text Available The packet loss has become an important issue to the research community, which needs to be addressed. In FMIPv6, Packet losses are significantly related to the handover latency and buffer size used for packet buffering. In the case of increased handover latency or decreased buffer size, packet losses will be increased. To solve the problem, we propose an adaptive packet buffering (APT algorithm based on priority of packets and traffic throughput in layer 3 (L3 were the packets are buffered by the predefined rule in the new access point during handover. This algorithm is designed to reduce packet loss in FMIPv6 and high level of throughput and low delay can be achieved through the proposed technique. To achieve a fair comparison with Adaptive Buffer Limit Tuning (ALT algorithm, we have implemented the APT algorithm in Omnet++ along with the FMIPv6 to develop the model and the algorithm. The results of the simulation study show that the proposed algorithm can reduce the packet loss as well as the delay.
Funk, W. C.; Murphy, M.A.; Hoke, K. L.; Muths, Erin L.; Amburgey, Staci M.; Lemmon, Emily M.; Lemmon, A. R.
2016-01-01
Evolutionary theory predicts that divergent selection pressures across elevational gradients could cause adaptive divergence and reproductive isolation in the process of ecological speciation. Although there is substantial evidence for adaptive divergence across elevation, there is less evidence that this restricts gene flow. Previous work in the boreal chorus frog (Pseudacris maculata) has demonstrated adaptive divergence in morphological, life history and physiological traits across an elevational gradient from approximately 1500–3000 m in the Colorado Front Range, USA. We tested whether this adaptive divergence is associated with restricted gene flow across elevation – as would be expected if incipient speciation were occurring – and, if so, whether behavioural isolation contributes to reproductive isolation. Our analysis of 12 microsatellite loci in 797 frogs from 53 populations revealed restricted gene flow across elevation, even after controlling for geographic distance and topography. Calls also varied significantly across elevation in dominant frequency, pulse number and pulse duration, which was partly, but not entirely, due to variation in body size and temperature across elevation. However, call variation did not result in strong behavioural isolation: in phonotaxis experiments, low-elevation females tended to prefer an average low-elevation call over a high-elevation call, and vice versa for high-elevation females, but this trend was not statistically significant. In summary, our results show that adaptive divergence across elevation restricts gene flow in P. maculata, but the mechanisms for this potential incipient speciation remain open.
Systemic Approach to Traffic Evaluation of Mostar Airport
Directory of Open Access Journals (Sweden)
Eldo Raguž
2005-11-01
Full Text Available The attempt of this work is to systematically find solutionsfor Mostar Airport development through technical and technologicalharmonization of traffic processes undertaken in twoseparate organizations - airport and air traffic control and coordinationbetween other traffic branches. The work uses theindicators of traffic flows and tourist trends in the region, andtogether with the mentioned simulations it attempts to evaluatethe traffic potentials in the region by affecting the change in thecurrent negative traffic flows at Mostar Airport.
Directory of Open Access Journals (Sweden)
Junbin Guo
2014-08-01
Full Text Available Preceding vehicle detection and tracking at nighttime are challenging problems due to the disturbance of other extraneous illuminant sources coexisting with the vehicle lights. To improve the detection accuracy and robustness of vehicle detection, a novel method for vehicle detection and tracking at nighttime is proposed in this paper. The characteristics of taillights in the gray level are applied to determine the lower boundary of the threshold for taillights segmentation, and the optimal threshold for taillight segmentation is calculated using the OTSU algorithm between the lower boundary and the highest grayscale of the region of interest. The candidate taillight pairs are extracted based on the similarity between left and right taillights, and the non-vehicle taillight pairs are removed based on the relevance analysis of vehicle location between frames. To reduce the false negative rate of vehicle detection, a vehicle tracking method based on taillights estimation is applied. The taillight spot candidate is sought in the region predicted by Kalman filtering, and the disturbed taillight is estimated based on the symmetry and location of the other taillight of the same vehicle. Vehicle tracking is completed after estimating its location according to the two taillight spots. The results of experiments on a vehicle platform indicate that the proposed method could detect vehicles quickly, correctly and robustly in the actual traffic environments with illumination variation.
Multi-level adaptive simulation of transient two-phase flow in heterogeneous porous media
Chueh, C.C.
2010-10-01
An implicit pressure and explicit saturation (IMPES) finite element method (FEM) incorporating a multi-level shock-type adaptive refinement technique is presented and applied to investigate transient two-phase flow in porous media. Local adaptive mesh refinement is implemented seamlessly with state-of-the-art artificial diffusion stabilization allowing simulations that achieve both high resolution and high accuracy. Two benchmark problems, modelling a single crack and a random porous medium, are used to demonstrate the robustness of the method and illustrate the capabilities of the adaptive refinement technique in resolving the saturation field and the complex interaction (transport phenomena) between two fluids in heterogeneous media. © 2010 Elsevier Ltd.
Adaptive mixed finite element methods for Darcy flow in fractured porous media
Chen, Huangxin; Salama, Amgad; Sun, Shuyu
2016-10-01
In this paper, we propose adaptive mixed finite element methods for simulating the single-phase Darcy flow in two-dimensional fractured porous media. The reduced model that we use for the simulation is a discrete fracture model coupling Darcy flows in the matrix and the fractures, and the fractures are modeled by one-dimensional entities. The Raviart-Thomas mixed finite element methods are utilized for the solution of the coupled Darcy flows in the matrix and the fractures. In order to improve the efficiency of the simulation, we use adaptive mixed finite element methods based on novel residual-based a posteriori error estimators. In addition, we develop an efficient upscaling algorithm to compute the effective permeability of the fractured porous media. Several interesting examples of Darcy flow in the fractured porous media are presented to demonstrate the robustness of the algorithm.
An adaptive mechanism to guarantee the bandwidth fairness of TCP flows
Institute of Scientific and Technical Information of China (English)
张顺亮; 叶澄清
2004-01-01
End-to-end TCP(transmission control protocol)congestion control can cause unfairness among multiple TCP connections with different RTT(Round Trip Time). The throughput of TCP connection is inversely proportional to its RTT.To resolve this problem,researchers have proposed many methods. The existing proposals for RTT-aware conditioner work well when congestion level is low. However,they over-protect long RTT flows and starve short RTT flows when congestion level is high. Due to this reason,an improved method based on adaptive thought is proposed. According to the congestion level of networks,the mechanism can adaptively adjust the degree of the protection to long RTT flows. Extensive simulation experiments showed that the proposed mechanism can guarantee the bandwidth fairness of TCP flows effectively and outperforms the existing methods.
An adaptive mechanism to guarantee the bandwidth fairness of TCP flows
Institute of Scientific and Technical Information of China (English)
张顺亮; 叶澄清
2004-01-01
End-to-end TCP (transmission control protocol) congestion control can cause unfairness among multiple TCP connections with different RTT (Round Trip Time). The throughput of TCP connection is inversely proportional to its RTT. To resolve this problem, researchers have proposed many methods. The existing proposals for RTT-aware conditioner work well when congestion level is low. However, they over-protect long RTT flows and starve short RTT flows when congestion level is high. Due to this reason, an improved method based on adaptive thought is proposed. According to the congestion level of networks, the mechanism can adaptively adjust the degree of the protection to long RTT flows. Extensive simulation experiments showed that the proposed mechanism can guarantee the bandwidth fairness of TCP flows effectively and outperforms the existing methods.
Adaptive mixed finite element methods for Darcy flow in fractured porous media
Chen, Huangxin
2016-09-21
In this paper, we propose adaptive mixed finite element methods for simulating the single-phase Darcy flow in two-dimensional fractured porous media. The reduced model that we use for the simulation is a discrete fracture model coupling Darcy flows in the matrix and the fractures, and the fractures are modeled by one-dimensional entities. The Raviart-Thomas mixed finite element methods are utilized for the solution of the coupled Darcy flows in the matrix and the fractures. In order to improve the efficiency of the simulation, we use adaptive mixed finite element methods based on novel residual-based a posteriori error estimators. In addition, we develop an efficient upscaling algorithm to compute the effective permeability of the fractured porous media. Several interesting examples of Darcy flow in the fractured porous media are presented to demonstrate the robustness of the algorithm.
基于自适应临界状态的交通流运营安全评价%Safety Audit of Traffic Flows Based on Self-adjustable Critical State
Institute of Scientific and Technical Information of China (English)
蒋锐; 郭忠印; 孔令旗
2011-01-01
考虑实际交通流中车辆驾驶员的主观能动性,改进交通冲突技术机械式假设的不足,提出交通流自适应临界状态概念.构建车速差、减速度差和行程时间差等3个模型,量化交通流运营状态的自适应“能力”.以安全车头时距和实际车头时距的差值,评价实时交通流运营安全性.通过实验分析,结果表明基于自适应临界状态的运营风险与历史事故数之间存在良好的相关性.%Considering characteristic of driver subjective in real traffic flows, self-adjustable critical state is put forward firstly conquering mechanical-hypothesis weakness of traffic conflict. Based on differences of speed/deceleration/travel time, analysis models are found to appraise ability of self-adjustable traffic flows. In according to discrepancy between safety headway and realistic headway, traffic flow risk index is introduced to audit real-time traffic safety. Experiment results showed that the relation between traffic flow risk and historical accidents is well.
Shallow sediment transport flow computation using time-varying sediment adaptation length
Institute of Scientific and Technical Information of China (English)
Jaan Hui PU; Khalid HUSSAIN; Song-dong SHAO; Yue-fei HUANG
2014-01-01
Based on the common approach, the adaptation length in sediment transport is normally estimated astemporally independent. However, this approach might not be theoretically justified as the process of reaching the sediment transport equilibrium stage is affected by the flow conditions in time, especially for fast moving flows, such as scour-hole developing flows. In this study, the two-dimensional (2D) shallow water formulation together with a sediment continuity-concentration (SCC) model were applied to flow with mobile sediment boundary. A time-varying approach was proposed to determine the sediment transport adaptation length to simulate the sediment erosion-deposition rate. The proposed computational model was based on the Finite Volume (FV) method. The Monotone Upwind Scheme of Conservative Laws (MUSCL)-Hancock scheme was used with the Harten Lax van Leer-contact (HLLC) approximate Riemann solver to discretize the FV model. In the flow applications of this paper, a highly discontinuous dam-break, fast sediment transport flow was used to calibrate the proposed time-varying sediment adaptation length model. Then the calibrated model was further applied to two separate experimental sediment transport flow applications documented in the literature, i.e. a highly concentrated sediment transport flow in a wide alluvial channel and a sediment aggradation flow. Good agreement with the experimental data were obtained with the proposed model simulations. The tests prove that the proposed model, which was calibrated by the discontinuous dam-break bed scouring flow, also performed well to represent rapid bed change and steady sediment mobility conditions.
Arnaout, Georges M.; Bowling, Shannon R.
2011-01-01
Traffic congestion is an ongoing problem of great interest to researchers from different areas in academia. With the emerging technology for inter-vehicle communication, vehicles have the ability to exchange information with predecessors by wireless communication. In this paper, we present an agent-based model of traffic congestion and examine the impact of having CACC (Cooperative Adaptive Cruise Control) embedded vehicle(s) on a highway system consisting of 4 traffic lanes without overtaking. In our model, CACC vehicles adapt their acceleration/deceleration according to vehicle-to-vehicle inter-communication. We analyze the average speed of the cars, the shockwaves, and the evolution of traffic congestion throughout the lifecycle of the model. The study identifies how CACC vehicles affect the dynamics of traffic flow on a complex network and reduce the oscillatory behavior (stop and go) resulting from the acceleration/deceleration of the vehicles.
Institute of Scientific and Technical Information of China (English)
陈晨; 陈建桥
2011-01-01
According to the theory of cellular automata ( CA), the urban traffic flows at 4 intersections were investigated and a set of discrete equations were proposed to describe the traffic dynamics. The effect of two signal control strategies, i.e., synchronous timing control and actuated control, on traffic flow were discussed. Simulation results show that ( 1 ) the effect of signal control strategies is related to the density of traffic flow; (2) and there exists a certain range of actuated control parameters in which the efficiency of traffic flow can be optimized. Therefore, in order to ensure the efficiency of traffic flow, one the proper signal control strategy should be chosen for different global densities of traffic flow.%采用细胞自动机方法(Cellular Automata:CA)模拟含4个路口的城市道路交通流状态,并通过离散方程描述车辆的运动过程.研究了信号灯控制策略(同步定时控制及感应控制)对交通流状态的影响.数值模拟结果表明,信号灯对交通流的影响与道路中车辆密度有关,同时,感应控制参数的选取存在一合理的取值范围,可优化交通流通行效率.因此,为保证交通流的通行效率,应针对不同的车辆密度,选取适当的信号灯控制方式.
Percolation properties in a traffic model
Wang, Feilong; Xu, Xiaoyun; Wu, Ruoqian; Havlin, Shlomo
2015-01-01
As a dynamical complex system, traffic is characterized by a transition from free flow to congestions, which is mostly studied in highways. However, despite its importance in developing congestion mitigation strategies, the understanding of this common traffic phenomenon in a city-scale is still missing. An open question is how the traffic in the network collapses from a global efficient traffic to isolated local flows in small clusters, i.e. the question of traffic percolation. Here we study the traffic percolation properties on a lattice by simulation of an agent-based model for traffic. A critical traffic volume in this model distinguishes the free-state from congested state of traffic. Our results show that the threshold of traffic percolation decreases with increasing traffic volume and reaches a minimum value at the critical traffic volume. We show that this minimal threshold is the result of longest spatial correlation between traffic flows at the critical traffic volume. These findings may help to dev...