Characteristics of Traffic Flow at Nonsignalized T-Shaped Intersection with U-Turn Movements

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

Modeling Left-Turn Driving Behavior at Signalized Intersections with Mixed Traffic Conditions

In many developing countries, mixed traffic is the most common type of urban transportation; traffic of this type faces many major problems in traffic engineering, such as conflicts, inefficiency, and security issues. This paper focuses on the traffic engineering concerns on the driving behavior of left-turning vehicles caused by different degrees of pedestrian violations. The traffic characteristics of left-turning vehicles and pedestrians in the affected region at a signalized intersection were analyzed and a cellular-automata-based “following-conflict” driving behavior model that mainly addresses four basic behavior modes was proposed to study the conflict and behavior mechanisms of left-turning vehicles by mathematic methodologies. Four basic driving behavior modes were reproduced in computer simulations, and a logit model of the behavior mode choice was also developed to analyze the relative share of each behavior mode. Finally, the microscopic characteristics of driving behaviors and the macroscopic parameters of traffic flow in the affected region were all determined. These data are important reference for geometry and capacity design for signalized intersections. The simulation results show that the proposed models are valid and can be used to represent the behavior of left-turning vehicles in the case of conflicts with illegally crossing pedestrians. These results will have potential applications on improving traffic safety and traffic capacity at signalized intersections with mixed traffic conditions

A discrete simulation model for heterogeneous traffic including bicycles on urban road networks

Environment and health-related concerns mean that pedal-bicycles as an alternative mode of urban transport are gaining ground, with study of motorised/non-motorised traffic mix a topic of practical interest in transportation science and traffic modelling. This thesis reports on a simulation model, developed for heterogeneous traffic on city networks with AD HOC lane-sharing, characteristic of Dublin streets. While based on simple cellular automaton rules, the vehicle movement model also accounts for vehicle type heterogeneity and network-specific factors, including the resolution of conflicts and effects of driver decisions on movement dynamics. The model has been implemented as an agent-based simulation framework. Its spatial component is based on a modular design that facilitates straightforward scenario configuration and scalability. In order to perform large network simulations, the framework has been adapted for parallel processing. Issues of both static and dynamic load balancing are considered. While detailed field data are not available for heterogeneous traffic on urban networks, which precludes precise quantitative validation, sensitivity analysis of the model was performed with a wide range of parameters and values. Macroscopic whole-network measures are defined and used to study a number of scenarios, the most manifest property of which is the contrast between slow and fast, vulnerable and less vulnerable agents in the traffic mix

TOWARDS MODELING DRIVER BEHAVIOR UNDER EXTREME CONDITIONS

The purpose of this study is to investigate the representation of driver behavior under extreme conditions, towards development of a micro-simulation modeling framework of traffic flow to support evaluation of management strategies and measures in emergency situations. To accomplish this objective, particular attention is given to understanding and representing "panic behavior" of individuals and how this behavior may be translated into driver actions. Related background from psychology and sociology is examined. Following a systematic review of previous traffic models, a model is selected as a starting point for modification towards the micro-simulation of traffic flow under extreme conditions. The model is based on Gipps' (1981) Car-Following Model. To evaluate the proposed modification, a prototype implementation is proposed for the micro-simulation of traffic flow on a stretch of highway with simplified geometric features. The vehicle trajectories and aggregate traffic properties are evaluated with respect to different scenarios through a sensitivity analysis

Book of abstracts of the 24th Euro Working Group on Transportation Meeting

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Dynamic Vehicular Routing in Urban Environments

Traffic congestion is a persistent issue that most of the people living in a city have to face every day. Traffic density is constantly increasing and, in many metropolitan areas, the road network has reached its limits and cannot easily be extended to meet the growing traffic demand. Intelligent Transportation System (ITS) is a world wide trend in traffic monitoring that uses technology and infrastructure improvements in advanced communication and sensors to tackle transportation issues such as mobility efficiency, safety, and traffic congestion. The purpose of ITS is to take advantage of all available technologies to improve every aspect of mobility and traffic. Our focus in this thesis is to use these advancements in technology and infrastructure to mitigate traffic congestion. We discuss the state of the art in traffic flow optimization methods, their limitations, and the benefits of a new point of view. The traffic monitoring mechanism that we propose uses vehicular telecommunication to gather the traffic information that is fundamental to the creation of a consistent overview of the traffic situation, to provision real-time information to drivers, and to optimizing their routes. In order to study the impact of dynamic rerouting on the traffic congestion experienced in the urban environment, we need a reliable representation of the traffic situation. In this thesis, traffic flow theory, together with mobility models and propagation models, are the basis to providing a simulation environment capable of providing a realistic and interactive urban mobility, which is used to test and validate our solution for mitigating traffic congestion. The topology of the urban environment plays a fundamental role in traffic optimization, not only in terms of mobility patterns, but also in the connectivity and infrastructure available. Given the complexity of the problem, we start by defining the main parameters we want to optimize, and the user interaction required, in order to achieve the goal. We aim to optimize the travel time from origin to destination with a selfish approach, focusing on each driver. We then evaluated constraints and added values of the proposed optimization, providing a preliminary study on its impact on a simple scenario. Our evaluation is made in a best-case scenario using complete information, then in a more realistic scenario with partial information on the global traffic situation, where connectivity and coverage play a major role. The lack of a general-purpose, freely-available, realistic and dependable scenario for Vehicular Ad Hoc Networks (VANETs) creates many problems in the research community in providing and comparing realistic results. To address these issues, we implemented a synthetic traffic scenario, based on a real city, to evaluate dynamic routing in a realistic urban environment. The Luxembourg SUMO Traffic (LuST) Scenario is based on the mobility derived from the City of Luxembourg. The scenario is built for the Simulator of Urban MObiltiy (SUMO) and it is compatible with Vehicles in Network Simulation (VEINS) and Objective Modular Network Testbed in C++ (OMNet++), allowing it to be used in VANET simulations. In this thesis we present a selfish traffic optimization approach based on dynamic rerouting, able to mitigate the impact of traffic congestion in urban environments on a global scale. The general-purpose traffic scenario built to validate our results is already being used by the research community, and is freely-available under the MIT licence, and is hosted on GitHub

Simulação do tráfego de veículos usando autômatos celulares

Orientador : Profa. Dra. Liliana Madalena GramaniCoorientador : Prof. Dr. Eloy KaviskiTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Métodos Numéricos em Engenharia. Defesa: Curitiba, 24/04/2015Inclui referências : f. 102-106Área de concentração : Programação matemáticaResumo: Esta tese propôe um modelo para o tráfego de veículos em uma pista com duas faixas, que considera o comportamento do motorista. Os principais modelos encontrados na literatura apresentam em sua estrutura equações diferenciais ou integro-diferenciais que exigem muitas variáveis para calibração do modelo. Por isso, usa-se neste trabalho a modelagem computacional via autômatos celulares. Os autômatos celulares possuem uma estrutura bastante simples e são capazes de modelar diversos fenômenos complexos por meio de regras simples. Sendo assim, desenvolveu-se um modelo de tráfego em uma pista com duas faixas onde avalia-se a mudança do comportamento do motorista a medida em que a densidade da via aumenta. Os perfis considerados neste trabalho são: Calmo, Moderado, Agitado e Agressivo. Esta análise é baseada na modelagem de um parâmetro a em função da densidade, utilizando uma distribuição de probabilidade contínua. Este parâmetro é utilizado para o cálculo da distância efetiva entre dois veículos permitindo o ajuste da velocidade do veículo detrás baseado no seu comportamento. O modelo também considera regras de mudanças de faixas assimétricas baseadas na evolução do comportamento adotado para melhor representar o fenômeno do fluxo de tráfego. Os resultados do modelo proposto mostraram-se satisfatórios quando comparados com outros modelos que consideram o comportamento do motorista em suas regras. A modelagem proposta para o comportamento do motorista resultou em um modelo que possibilita descrever a alteração no comportamento do motorista quando a densidade é aumentada. Palavras-chave: simulação computacional, tráfego de veículos, autômatos celulares, comportamento do motorista.Abstract: This thesis proposes a model for the traffic of vehicles on a double lane track, which considers the driver's behavior. The main models found in literature present in its structure differential or integro-differential equations that require many variables for model calibration. Therefore, in this work, computational modeling via cellular automata is used. The cellular automata have a very simple structure and are capable to model several complex phenomena through simple rules. Thus, a traffic model was developed on a double lane track where the driver's behavior change is evaluated as the track density increases. The profiles considered in this work are: Calm, Moderate, Agitated and Aggressive. This analysis is based on the modeling of a parameter around density, using a continuous probability distribution. This parameter is used to calculate the effective distance between two vehicles, allowing the adjustment of the speed of the vehicle behind based on its behavior. The model also considers rules of asymmetric track changes based on the evolution of the adopted behavior to better represent the traffic flow phenomenon. The results of the model were satisfactory when compared to other models that consider the driver's behavior in your rules. The proposed modeling for driver behavior resulted in a model that allows to describe the change in driver behavior when the density is increased. Key-words: computational simulation, vehicular traffic, cellular automata, driver behavior

Eine mikrosimulationsbasierte Methode zur Beurteilung der Leistungsfähigkeit von Shared Space

Shared space is a concept of urban street design which implies the creation of a level surface within the whole road reserve and is aimed at encouraging different road users to interact spontaneously and to negotiate priority with each other. To build successful shared spaces, traffic engineers can rely at present on specific guidelines as well as technical reports. Nevertheless, there is no method available to compute the performance of shared spaces in terms of Level Of Service (LOS). In order to address this gap, a new indicator of traffic quality for pedestrians is being developed. This measure of performance considers aspects of comfort related to the crossing, which pedestrians use to go from one side of the roadway to the other. During this movement, discomfort is generated by the necessity to solve the conflicts with vehicles. Therefore, factors which potentially influence comfort are mathematically formulated. Later, the performance indicator can be calibrated on the basis of the opinion of a group of respondents, who evaluated real-world crossing movements in video sequences. The effectiveness and usability of the developed indicator is demonstrated in an exemplary case study. A shared street in the district of Bergedorf, Hamburg (D) is selected and filmed. To reproduce the interaction of road users and the mechanism of space negotiation, an innovative modeling approach based on social force model (SFM) is proposed. The model is calibrated and implemented in a Java-based simulation tool. Alternative shared space scenarios, as well as conventional ones with space segregation, are simulated. The goal of this dissertation is to establish a method to evaluate the performances of shared spaces through traffic microsimulation. This method includes the data survey and acquisition, the definition of performance indicators, the development of a microsimulation approach, the calibration of the motion model on the basis of real-world data and finally the execution of simulations to collect the results. In addition, this work shows the necessity to employ a comfort-based indicator for pedestrian traffic quality in shared spaces. The benefits of this approach, with respect to conventional efficiency-based indicators as time delay, is properly shown in real-world situations and successively demonstrated by help of statistical methods.Shared Space ist ein Konzept der urbanen Straßengestaltung, das die Schaffung von niveaugleichen Zonen im gesamten Straßenquerschnitt beinhaltet, und darauf abzielt, die verschiedenen Verkehrsteilnehmer zu ermutigen, spontan zu interagieren und den Vorrang untereinander auszuhandeln. Um erfolgreiche Shared Spaces zu gestalten, können sich Ingenieure derzeit auf spezifische Richtlinien, sowie auf technische Berichte stützen. Dennoch gibt es keine Methode, um die Qualität des Shared Space im Hinblick auf den Level of Service (LOS) zu kalkulieren. Daher wird ein neuer Verkehrsqualitätsindikator für Fußgänger entwickelt. Diese Erfolgsmessgröße berücksichtigt Komfortaspekte hinsichtlich der von Fußgängern zur Querung der Straßen benutzten Übergänge. Während der Überquerung wird durch das Aushandeln des Vorrangs mit den Fahrzeugen ein Unbehagen erzeugt. Daher werden potentiell komfortbeeinflussende Faktoren mathematisch formuliert. Später kann der Leistungsindikator auf Basis der Ansicht einer Umfragegruppe, die reale Straßenüberquerungen in Videosequenzen auswertet, kalibriert werden. Die Effektivität und Tauglichkeit des entwickelten Indikators wird in einer exemplarischen Fallstudie im Hamburger Bezirk Bergedorf demonstriert. Hierzu wird der dortige Shared Space gefilmt. Um die Interaktion von Verkehrsteilnehmern und die Wirkungsweise der Verkehrsraumaushandlung nachzustellen, wird ein innovativer Modellierungsansatz, der auf dem sozialen Kräftemodell basiert, empfohlen. Das Modell wird in einem Java-basierten Simulationstool kalibriert und implementiert. Verschiedene Shared Space Arten und konventionelle Szenarien mit Raumtrennung werden simuliert. Das Ziel dieser Dissertation ist es, ein Verfahren zur Auswertung der Performances von Shared Spaces durch Verkehrsmikrosimulation zu entwickeln. Dieses Verfahren beinhaltet die Datenerhebung und –erfassung, die Definition der Leistungsindikatoren, die Entwicklung eines Mikrosimulationsansatzes und die Kalibrierung des Bewegungsmodells auf Basis realer Daten. Zudem werden Simulationen durchgeführt, um Ergebnisse zu sammeln. Des Weiteren zeigt diese Arbeit die Notwendigkeit, einen komfortbasierten Indikator für die Verkehrsqualität der Fußgänger in Shared Spaces zu verwenden. Die Vorteile dieses Ansatzes, gegenüber konventionellen, effizienzbasierten Indikatoren wie z.B. Zeitverzögerungen, werden entsprechend in praxistauglichen Situationen dargestellt und sukzessiv mittels statistischer Verfahren veranschaulicht

GPU Accelerated Simulation of Transport Systems

Computer modelling and simulation of road networks are a vital tool used to evaluate, design and manage road network infrastructure. Road network simulations are however computationally expensive, with simulation runtime imposing limits on the scale and quantity of simulations performed within a reasonable time frame. This thesis examines the appropriateness of many-core processing architectures (such as GPUs) for the acceleration of microscopic and macroscopic road network simulation, and the potential impact on the choice of modelling approach. Fine-grained agent-based microscopic simulations of individual vehicles are parallelised using GPUs, achieving high performance through a novel graph-based communication strategy for data-parallel simulations. A minimal benchmark model and scalable road network are defined and used experimentally to evaluate performance compared to Aimsun, a commercial simulation tool for multi-core processors. Performance improvements of up to 67x are demonstrated for large scale simulations. High-level macroscopic simulations model network flow rather than individual vehicles. Although less computationally demanding than microscopic models, simulation runtimes can still be significant, often due to the calculation of many shortest paths. A novel Many-Source Shortest Path (MSSP) algorithm is proposed to concurrently find multiple shortest paths through sparse transport networks using GPUs. This is embedded within a commercial multi-core CPU macroscopic simulation tool, SATURN, and the performance evaluated on large-scale real-world road networks, demonstrating assignment performance improvements of up to 8.6x when comparing multi-processor GPU and CPU implementations. Finally, the impact of the performance improvements to both modelling techniques are evaluated using a common benchmark model and the relative improvements demonstrated by the benchmarking of each approach using different transport networks. These results suggest that GPUs will allow modellers to shift towards using finer-grained simulations for a broader range of modelling tasks