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International audience; In urban environments, there are now many challenging problems concerning freight transport.As cities around the world grow rapidly, there is an increase in pickup-delivery truck traffic inurban areas. It turns out that commercial traffic is now a major source of externalities in metroareas, including congestion, noise, air pollution (small particulates, NOx, greenhouse gasemissions), and traffic incidents [1].To overcome these issues, many interesting and innovative strategies have been developed inEurope and other parts of the world. Especially, some researchers proposed the idea of citylogistics to solve these difficult problems [2-3]. The idea of this concept is to rationalize thefreight activities in cities by optimizing operations considering the traffic conditions and thecongestion issues. Consequently, public authorities strongly need decision support frameworksto evaluate urban logistics planning and management.It turns out that a key point in predicting the impacts of city logistics is the influence of freighton traffic flow dynamics. Particularly, pickup-delivery trucks maneuvers generate roadcapacity reduction and lead to delay for individual drivers. Although this is a crucial topic, theliterature rarely addresses this issue. This paper aims to fill this lack of understanding byincorporating the effects of urban freight in a traffic flow model.

IEEE 17th International Conference on Intelligent Transportation Systems ITSC, Qingdao, CHINE, 08-/10/2014 - 11/10/2014; The deployment of Electric Vehicles (EVs) is constrained mainly by the restricted autonomy, the lack of charging stations, the battery recharge time and recuperation capability (e.g. braking phases or downhill). In this study we aim to develop a green routing tool to encourage the use of EV. To overcome the autonomy limitation we propose a methodology for the EV that includes a charging stations location model, an energy graph construction for EV routing and a resolution scheme for the routing problem with recharging stage(s) along the way on the available charging stations.

TAP 2014, 20th Internationa conference on Transport and Air Pollution, GRAZ, AUTRICHE, 18-/09/2014 - 19/09/2014; Within the framework of MOCoPo research project, an in-situ experiment was conducted during one- month in Grenoble, France (400,000 inhabitants) on a high-capacity road (ring, 2x2 lanes) close to an area of exchanges and frequently under congested conditions. Traffic counting was performed at 6- minutes intervals. Four video-cameras were installed to capture in real-time vehicle license plates. Their identification through the national registrations enabled the characterization of the fleet composition. These data were used to simulate pollutant emissions from the traffic, by the COPCETE calculation plate-form. Based on the COPERT4 (V9) methodology, it enables the computation of around 7000 observations (i.e. two full weeks of valid 6-minutes data), integrated on a distance of 1 km, and described by the real-world traffic data (flow, speed) and fleet composition as observed by the video. These works have first enabled the implementation of the video technique to capture the in- situ fleet composition. 1.7 million of observations and 350,000 French registrations allowed a good and detailed characterization of the local fleet, its specificities and variability with the time-periods. Analyses of pollutant emissions demonstrate that they are mainly linked to the traffic flows, thus to the fleet composition (heavy vehicle share) and then to the traffic conditions. Complementary analyses demonstrate the importance of cold start over-emission.

The aim of this paper is to investigate an inverse method to reconstruct the dynamic demand in order to improve network modelling. This is a key point for traffic simulation. The traffic flow is modeled with the fisrt order LWR model. A functional to minimize has to be considered and the optimization variables correspond to boundary conditions describing the demand entering the network. Classical optimization techniques (Lagrange multipliers and descent method) are used to solve this problem.

International audience; In 2009, French authorities launched a national plan for the deployment of charging infrastructure in order to promote the electromobility. Key stakeholders and industrial such car manufacturers, energy distribution companies and researchers were encouraged to propose optimal solutions for the installation of charging stations (CS). These solutions should cover all types of configurations: public roads, parking, and workplace. The French Environmental and Energy Management Agency (ADEME) set standards and norms for the allocation of charging stations while drawing the roadmap to the expansion of these infrastructures. The latter included three key parameters for the establishment of a national charging network, which are: Standardization of the charging infrastructure: this includes all the issues such as the interoperability of charging structures, security, infrastructure competitiveness, user comfort and convenience, and an optimized management of the energy consumption. Regulatory framework and a viable business model to ensure the integration and success of the electric vehicles. This includes a vehicles cost reduction to assure future users of the viability of this technology (recycling battery component). Determination of an equilibrium between the location of the CS and the capacity of the electric vehicle battery in order to make the network more resilient to this type of mobility. Achieving a balance between these interactions is a key parameter to be taken into account in the strategy for the deployment of the charging infrastructure. In this report, one of the main points that should be emphasized is the standard that must be applied when designing a charging station infrastructure. Concerning the type of CS, three types of terminals are identified: (i) slow charging points for home or long stay parking charging, (ii) semi-rapid charging points mainly at public park and (iii) fast CS along urban motorways and dense road traffic. The expansion of Electric Vehicles (EV) implies an optimized and cost-effective deployment of CS. As a decision support tool for network design, we define a methodology to locate CS in a real case study network. This study uses OD matrix information from household travel survey mixed with a dynamic model to evaluate electric vehicles consumption based on realistic trips (urban cycles). These trips are computed based on routing tools and augmented with elevation information. This enables a characterization of energy needs in the City of Lyon. All these parameters are used as inputs of an integer linear model for the location of CS. The methodology adapts the classic fixed charge location model with a p-dispersion constraint. The results indicate that this methodology can help the future implementation of charging stations at an urban scale.

TRB 2014 - Transportation Research Board 93rd Annual Meeting, WASHINGTON D.C, ETATS-UNIS, 12-/01/2014 - 16/01/2014; Transilien, the branch of SNCF in charge of operating the main urban railroad network in the area of Paris, faces a regular increase of passengers flows. The planning of railway operations is made carefully: simulation runs permit to assess the timetable stability. However, many disturbance 5 appears and cause trains delays. Due to the nature of the railroad network those delays are cumulative and an on-line update of the timetable is not always successful in maintaining the trains schedule. In this tensed context, operators are searching solutions to better use the infrastructure capacity and better service quality. A needed step towards this objective is a better understanding of the phenomena of disruptions. In particular because the expansion of congestion is not clearly 10 understood until now. This paper explores the possibility to transpose a traffic flow theory tool, the network fundamental diagram, in the field of dense railroad traffic. Railroad traffic is different of road traffic by many ways: railways are a planned system, traffic volume does not satisfy the continuum hypothesis, stations force stops and the signalization system brings a discrete behavior. Despite those big differences we show how to build a network fundamental diagram for a railroad 15 system and how to interpret some obtained shapes for those diagrams. These diagrams gives us some means to compare planned and reality. We also identify the limits that need to be overcome to take benefits of the road traffic tools in railroad traffic analysis.

Drivers behave in different ways, and these different behaviors are a cause of traffic disturbances. A key objective for simulation tools is to correctly reproduce this variability, in particular for car-following models. From data collection to the sampling of realistic behaviors, a chain of key issues must be addressed. This paper discusses data filtering, robustness of calibration, correlation between parameters, and sampling techniques of acceleration-time continuous car-following models. The robustness of calibration is systematically investigated with an objective function that allows confidence regions around the minimum to be obtained. Then, the correlation between sets of calibrated parameters and the validity of the joint distributions sampling techniques are discussed. This paper confirms the need for adapted calibration and sampling techniques to obtain realistic sets of car-following parameters, which can be used later for simulation purposes.

ICCVE 2014, International Conference on Connected Vehicles and Expo, VIENNE, AUTRICHE, 03-/11/2014 - 07/11/2014; The deployment of Electric Vehicles (EVs) is constrained mainly by the limited battery capacity, the limited number of charging stations and the recharging time. Our goal is to promote the use of EV by developing energy-efficient routing tools. To overcome the autonomy limitation we propose a methodology for the EV routing problem with recharging stage(s) along the way on the available charging stations.

TRB 2014 - 93rd Transportation Research Board Annual Meeting, WASHINGTON DC, ETATS-UNIS, 12-/01/2014 - 16/01/2014; The travel time variability may significantly influence the driver's route choice. Estimating travel time reliability is thus really appealing to urban infrastructure managers. This could provide better information to drivers, encourage their reassignment on the network, and optimize its use. In this paper, we study any arterial in under-saturated conditions with known fixed-time traffic signals. The kinematic wave model is chosen to simply represent traffic dynamics. A semi-analytical (grid-free) method is applied to determine the separation between vehicle groups at each signal of the arterial. The main contribution of this paper is to present an aggregated diagram that describes the functioning of this arterial. It graphically provides the direct assessment of vehicle travel times with respect to their departure and the traffic flow. This tool only depends on signal settings and is cyclic and invariant for fixed-time signals. We show how to use this diagram to generate probabilistic travel time distributions when some input parameters are uncertain. Furthermore, this diagram appears insightful when the traffic flow is not accurately known.

The traffic engineering community currently faces the advent of a new generation of Intelligent Transportation Systems (ITS), known as cooperative systems. More specifically, the recent developments of connected and autonomous vehicles, i.e. cooperative vehicles, are expected to cause a societal shift, changing the way people commute on a daily basis and relate to transport in general. The research presented in this dissertation is motivated by the need for proper understanding of the possible inputs of cooperative vehicles in a traffic stream. Beyond legal aspects regarding the introduction of such vehicles and considerations on standardization and harmonization of the communication norms, the research focuses on the use of communication for highway traffic flow homogenization. In particular, the selected approach for the introduction of cooperation inherits from the theory of traffic flow and the recent developments of microscopic traffic models. Cooperation can first be introduced as a form of multi-anticipation, which can either come from drivers' behaviors or from communication. A mathematical framework for investigating the impact of perturbations into a steady-state traffic is proposed for the class of time continuous car-following models. Linear stability analyses are refined for forward and backward multi-anticipation, exploring the underlying importance of considering upstream information. The linear stability analyses for all wavelengths can be deepened by the mean of the graphical root locus analysis, which enables comparisons and design of strategies of cooperation. The positive influence of bilateral cooperation and of added linear control terms are highlighted. Weakly non-linear analyses are also performed, and the equations of solitary waves appearing at the frontier of the instability domain are obtained. A simple condition over the partial derivatives of the dynamical system is found to determine the acceleration regime of the leading edge of the travelling wave. Following these analytical results, one aim is to simulate a realistic traffic thereby reproducing the driving behavior variability. A Next Generation Simulation trajectory dataset is used to calibrate three continuous car-following models. A methodology involving data filtering, robust calibration, parameters estimation and sampling of realistic parameters is detailed, and allows realistic traffic with stop-and-go waves appearances to be replicated. Based on these simulated trajectories, previous analytical results are confirmed, and the growing perturbations are removed for various coverage rates of cooperative vehicles and adequately tuned cooperative strategies. Finally the issue of information reliability is assessed for a mixed fleet of cooperative and non-cooperative vehicles. The modeling choice consists in building a three layers multi-agent framework that enables the following properties to be defined: the physical behavior of vehicles, the communication possibilities, and the trust each vehicle -or agent- has in another vehicle information or in itself. The investigation of trust and communication rules allow the model to deal with high rates of disturbed cooperative vehicles sensors and to learn in real time the quality of the sent and received information. It is demonstrated that appropriate communication and trust rules sensibly increase the robustness of the network to perturbations coming from exchanges of unreliable information.

Exposure to noise may constitute a health risk examined in epidemiologic studies. Indeed, we do not get used to noise but cumulate its effects. Furthermore, noise with highly variable levels increases the negative impacts. In urban areas, such situations are common due to traffic dynamics. On the other hand, in operational studies, one has typically to estimate the noise level at the building frontage, in application of French environmental noise regulation. In this work, we would like to adopt another point of view. We want to focus on the noise exposure of pedestrians during their displacements in urban areas, rather than the exposure of people when they are inside a building. The case study is a section of an urban boulevard with six traffic lights. The method developed in this work relies on a predefined set of receivers and the calculation of the dynamic noise levels at such locations. We can then assess the whole exposure of the pedestrian during his route. Several routes have been analyzed and characterized using traditional and dynamical indicators., L'exposition au bruit a une incidence sur la santé des individus, telles que le démontrent les études épidémiologistes. En milieu urbain, la situation est d'autant plus critique que la dynamique du trafic routier y impose de fortes variations des niveaux sonores auxquelles nous sommes sensibles et des niveaux sonores élevés pour lesquels nous cumulons les effets négatifs au cours de la journée. D'autre part, les études d'impact réglementaires cherchent à estimer les niveaux sonores en façade des bâtiments afin de limiter l'exposition de leurs occupants, mais ne se préoccupent pas de l'exposition des piétons. La méthode décrite dans cet article permet de déterminer la dose de bruit perçu par un piéton parcourant un boulevard urbain à partir d'une simulation dynamique couplée trafic - bruit, en s'appuyant sur un maillage de récepteurs prédéfini. Les résultats analysés nous permettent de caractériser l'exposition des piétons en fonction de leur trajet à l'aide d'indicateurs traditionnels et dynamiques.

The purpose of the flagship project Crossing Borders is the development and testing of cross-border services for electric mobility. A cross-border fast charging network, roaming and billing system and intermodal routing services will be implemented in cooperation with partners from Austria, Germany and Slovakia. On one hand, the market success of electric mobility will depend on the availability of high grade services for users. On the other hand, the users' motivation to choose alternate forms of mobility, to make informed mobility-based decisions and to explore novel mobility options is an essential step in reaching a significant momentum in electric mobility. However, the availability of electric mobility options must be met with suitable tools that inform and support the users. With this in mind, workpackage 5 (WP5) focuses on the question of what type of bonification, incentives and gamification mechanics will produce substantial change in mobility behavior. Based on state of the art research in playful incentive systems (f.e. gamification, serious games and game mechanics) a novel approach to explore the potential of games in the area of mobility will be undertaken.

TRA 2014 - Transport Research Arena : 5th Conference: Transport Solutions from Research to Deployment, PARIS , FRANCE, 14-/04/2014 - 17/04/2014; The evolution towards electromobility has been an extensive topic of interest in the last years. This evolution is driven by the environmental potential benefits of the plug-in electric vehicles (EV's) commercially produced and the rise of hydrocarbon cost which induces the search for alternative solutions to break mobility dependence on fossil fuels. However, a large-scale electromobility deployment will bring up new challenges and several research issues such as the optimal charging stations allocation, the battery recharge time and the autonomy constraints. Many researchers and stakeholders have been interested in the design and standardization of charging stations and the optimal location of charging stations problem.This work focuses on the facilities location/allocation models which consist on defining the best candidate site, the type and the size (number of terminal) of the charging stations to be assigned in the network (mainly in urban area) in order to satisfy a given mobility demand (converted into electric needs). First, this paper will provide the taxonomy of a wide spectrum of discrete allocation/location models where the formulation of three foundational discrete families of location models is reviewed: Coverage, Median and Dispersion models. Moreover, algorithm solutions were discussed. Then, the stochastic class of these models is introduced. Finally, the recent application of the location models for alternative fuel charging station is discussed in this paper.

Les objectifs de cette dernière tâche sont multiples. Dans un premier temps, il s'agit de réaliser une synthèse et une mise en perspective des résultats obtenus par les trois autres tâches de travail. Cette synthèse des différentes dimensions (usages, technologiques et simulation) permet d'établir des préconisations préliminaires pour assurer l'efficacité du système ADViCe pour un site donné. Des critères d'éligibilité portant sur les caractéristiques des sites recensés pourront être définis. Ils porteront sur les différentes dimensions identifiées en T1 : géométrie et topologie du site (type de voirie, d'intersection, étendue spatiale du site, etc.), scénarios de trafic (amplitude spatiale, durée de la perturbation, etc.), compatibilité et acceptabilité (réseau de TC existant, intégration au système de régulation existant, etc.) et la réglementation en vigueur. Ces critères permettront de préciser les technologies ainsi que les IHM associées à mettre en place pour un site donné mais aussi les paramètres efficaces d'une stratégie ADViCe (seuils de déclenchements, l'horizon temporel, l'étendue spatiale, etc.). Pour ce faire, nous utiliserons comme fil rouge un des sites identifiés dans la T1. L'enjeu n'est pas l'équipement du site mais de mettre en avant des premières préconisations permettant d'assurer l'efficacité de la stratégie ADViCe.

This paper is a contribution towards an operational use of large floating car data (FCD) in traffic 47 management. The work focuses on a practice-ready approach on highways. The goal is to detect 48 in real-time the end of a perturbation. As an entire highway network is not fully equipped with 49 cameras or loop detectors, FCD have the potential to help better detect the end of a moving 50 bottleneck. This specific zone represents a significant road safety risk and there is a need for 51 better real-time detection of the end of congestion. To address this issue, real world data are 52 analyzed from a French freeway with recurrent congestion patterns. After discussing the quality 53 and precision of FCD, a dynamic spatial segmentation of the network highlights the relevance of 54 this data source from an operational standpoint. Further to the empirical network 55 characterization, a systematic detection algorithm is introduced, which is able to detect the 56 queue-end in real-time with a 500m precision. Based on the assumption of a growing penetration 57 rate of FCD in the coming years, the algorithm uses only FCD with very simple detection rules 58 and few parameters. The method is validated on real congestion cases and the results prove the 59 accuracy of the detection. A discussion about the precision of FCD and recommendations for 60 road operators are introduced.

A global framework for linear stability analyses of traffic models, based on the dispersion relation root locus method, is presented and is applied taking the example of a broad class of car following models. This approach is able to analyse all aspects of the dynamics: long waves and short wave behaviors, phase velocities and stability features. The methodology is applied to investigate the potential benefits of connected vehicles, i.e. V2V communication enabling a vehicle to send and receive information to and from surrounding vehicles. We choose to focus on the design of the coefficients of cooperation which weights the information from downstream vehicles. The coefficients tuning is performed and different ways of implementing an efficient cooperative strategy are discussed. Hence, this paper brings design methods in order to obtain robust stability of traffic models, with application on cooperative car following models.

A bus route is inherently unstable: in presence of traffic or for high passenger demands, buses fail to maintain their time-headways and so tend to bunch when the system is uncontrolled. Several bus motion models have been proposed to study the behavior of buses and evaluate regulation strategies. The ability of these models to reproduce the irregularity of bus systems comes only from stochasticity. Some recognized phenomena like a change of conditions during a day or delays at signalized intersections are ignored. This paper tries to fill this lack and provides an overview of existing dynamic bus-focused models. In a first time, commonly used deterministic and stochastic models are compared. That allows quantifying the relative influence of stochasticity of each model component on the regularity. Besides, previous works always consider routes in stationary conditions and assume that perturbations come only from stochasticity. Conversely, we show that a change of the system equilibrium leads to bus irregularity. Finally, this paper points out the inability of classical bus models to reproduce the effects of traffic signals. A refinement of travel time models is proposed to account for non- dynamic signals. Such a development could allow forecasting the bus route state in the case of Bus Rapid Transit.

This paper investigates the sensibility of pollutant estimations to errors when determining the traffic states at large urban scale. Two key figures are required to estimate traffic-related pollutants at this scale: the mean speed with the considered region and the travel production. Loop detectors and probes can be used to determine these variables. In this paper, the estimation methods for these variables and the influence of the sampling rate will be questioned. The analysis revealed that (i) probes data provide accurate results even for low sampling rate and that (ii) the precision of travel production's estimate is mainly linked to the precision of the sampling ratio's assessment. The latter will be approximated combining information from probes and loops., Cet article examine la sensibilité des estimations de polluants aux erreurs lors de la détermination des états de circulation à grande échelle en milieu urbain. Deux chiffres clés sont nécessaires pour estimer les polluants liés au trafic à cette échelle : la vitesse moyenne avec la région considérée et la production de déplacements. Des boucles de comptages et des véhicules traceurs peuvent être utilisés pour déterminer ces variables. Dans cet article, les méthodes d'estimation de ces variables et l'influence du taux d'échantillonnage seront remises en question. L'analyse a révélé que (i) les données des véhicules traceurs fournissent des résultats précis même pour un faible taux d'échantillonnage et que (ii) la précision de l'estimation de la production de déplacements est principalement liée à la précision de l'évaluation du taux d'échantillonnage. Ce dernier sera approximé en combinant les informations des véhicules traceurs et des boucles de comptages.

The deployment of Electric Vehicles (EVs) needs an optimized and cost-effective implementation of charging stations. As a decision support tool for network design, we define a methodology to allocate charging stations in a real network. This study uses trip OD matrix information from household travel survey coupled with a dynamic vehicle model to evaluate EVs consumption based on realistic trips (urban drive cycles). These trips are computed based on routing tools and supplied with elevation information. This enables an accurate characterization of energy needs in the Lyon Metropolitan Area. All these parameters are used as inputs of an integer linear optimization program for the location of charging stations. The methodology is based on an adaption of the classic fixed charge location model with a p-dispersion constraint. The results indicate that this methodology can help the future implementation of charging stations at an urban scale.

The expected future deployment of communication technologies, and the new generation of Intelligent Transportation Systems (ITS) known as cooperative systems bring lots of expectations in terms of vehicle traffic flow control and management. The numbers of interactions and exchanges between cars, and with the infrastructure can considerably grow, which as a result could carry new challenges to the traffic modeling community. In this paper we investigate the effects of cooperation between vehicles at a microscopic level, where communication is directly integrated into the car following law. Some linear stability analyses allow identifying regimes of potential propagation of shock waves into a traffic stream. Real data based simulation confirms the theoretical findings, and values of efficiency and safety indicators are discussed based on the chosen cooperative strategy.; Les avancées en technologies de la communication ont peu à peu donné naissance à une deuxième génération de Systèmes de transports intelligents (ITS) connus sous le nom de systèmes coopératifs. En permettant aux différents véhicules de communiquer entre eux ou à travers l'infrastructure, les systèmes coopératifs révolutionnent la gestion du trafic autant qu'ils la complexifient de par la richesse des possibilités qu'ils entrouvrent. L'implémentation prochaine de ces nouveaux services pose également un certain nombre de défis en modélisation du trafic qu'il convient d'anticiper. Dans cet article, nous proposons un effort d'intégration de quelques concepts de communication dans les modèles microscopiques de type loi de poursuite et les stratégies de changement de voie associées. Au niveau théorique, les analyses de stabilité montrent comment l'introduction d'une coopération permet, dans certaines situations, de limiter le développement d'ondes de type stop and go. Ces résultats sont ensuite illustrés en simulation à travers le calibrage de données réelles. Les expériences numériques permettent ainsi de conclure sur le potentiel stabilisant des systèmes coopératifs en situation de congestion. Des considérations sur le pourcentage de véhicules ou le rayon de communication permettent de fournir des premiers éléments d'aide à la décision en vue de futurs déploiements de ces nouvelles technologies.

The goal of this study is to highlight the effects of adverse weather conditions on traffic demand. The literature review underlines that some events, especially rain and snow, induce significant changes on both travel demand and traffic operations. These changes have several origins (modal shift, time departure postponement, travel cancellation. . .) and depend on many factors, such as time of day (day/night), week (weekdays/weekend), environment (urban/interurban area), trip purpose (discretionary/nondiscretionary). . . The literature review is therefore divided in two parts: a study of surveys that reveals the impact of weather on travel choices, and then statistical analysis conducted on traffic data collected from loop detectors. This preliminary work is completed by statistical analysis and modeling on operational interurban data (a section of the A43 French Highway) and urban data (route næ 3, Tokyo).; L'objectif de cet article est de mettre en évidence les effets de la météorologie sur la demande de trafic. Une étude approfondie de la littérature est d'abord réalisée : d'une part une analyse des conséquences sur la demande de déplacement au sens large à travers le prisme du modèle à quatre étapes (à partir d'enquêtes principalement) et d'autre part un focus sur la demande de trafic, en synthétisant les analyses réalisées à partir des données boucles. L'analyse montre ainsi que certains événements météorologiques, comme la pluie et surtout la neige, conduisent à des modifications dans les comportements (transfert modal, annulation du déplacement. . .) et à une baisse de la demande de trafic. La nature et l'amplitude des changements opérés dépendent de nombreux facteurs, comme la période du jour (journée/nuit), de la semaine (semaine/week-end), du milieu (urbain/interurbain), du motif du déplacement (contraint/non contraint). . . Cette bibliographie est ensuite complétée par des analyses statistiques et des modélisations sur des données opérationnelles recueillies en milieu interurbain (section Lyon-Chambéry de l'A43) et sur la route n 3 des autoroutes urbaines de Tokyo.

The goal of this study is to highlight the effects of adverse weather conditions on traffic demand. The literature review underlines that some events, especially rain and snow, induce significant changes on both travel demand and traffic operations. These changes have several origins (modal shift, time departure postponement, travel cancellation. . .) and depend on many factors, such as time of day (day/night), week (weekdays/weekend), environment (urban/interurban area), trip purpose (discretionary/nondiscretionary). . . The literature review is therefore divided in two parts: a study of surveys that reveals the impact of weather on travel choices, and then statistical analysis conducted on traffic data collected from loop detectors. This preliminary work is completed by statistical analysis and modeling on operational interurban data (a section of the A43 French Highway) and urban data (route næ 3, Tokyo).; L'objectif de cet article est de mettre en évidence les effets de la météorologie sur la demande de trafic. Une étude approfondie de la littérature est d'abord réalisée : d'une part une analyse des conséquences sur la demande de déplacement au sens large à travers le prisme du modèle à quatre étapes (à partir d'enquêtes principalement) et d'autre part un focus sur la demande de trafic, en synthétisant les analyses réalisées à partir des données boucles. L'analyse montre ainsi que certains événements météorologiques, comme la pluie et surtout la neige, conduisent à des modifications dans les comportements (transfert modal, annulation du déplacement. . .) et à une baisse de la demande de trafic. La nature et l'amplitude des changements opérés dépendent de nombreux facteurs, comme la période du jour (journée/nuit), de la semaine (semaine/week-end), du milieu (urbain/interurbain), du motif du déplacement (contraint/non contraint). . . Cette bibliographie est ensuite complétée par des analyses statistiques et des modélisations sur des données opérationnelles recueillies en milieu interurbain (section Lyon-Chambéry de l'A43) et sur la route n 3 des autoroutes urbaines de Tokyo.

The Three representation of traffic flow : The moving bottleneck theory ; Numerical issues. Godunov based numerical schemes : Moving bottlenecks in Eulerian coordinates ; Fixed bottlenecks in Lagrangian coordinates. Variational theory based numerical schemes : The shortcut principle : Applications to the three coordinate systems ; Related approaches (viability theory).

Evaluer et estimer la consommation énergétique des véhicules a toujours été un élément important lors de la détermination des émissions de CO2, gaz responsable de l'effet de serre. Plusieurs études se sont intéressées à l'évaluation de la consommation de tout type de véhicule (thermique, hybride ou encore électrique) avec comme objectif la réduction de la consommation. Cette dernière a un impact direct sur les émissions de CO2. L'éco-itinéraire représente notre première préoccupation et notre travail vise à développer des outils de routage et de calcul d'itinéraire économe en énergie afin de promouvoir l'usage des véhicules électriques. Il faut rappeler que plusieurs éléments freinent l'essor de ce type de mobilité routière dont les plus significatifs sont l'autonomie, le manque de stations de recharge, le temps de rechargement et la capacité de récupération. Cette dernière, bien qu'elle présente un avantage en termes d'économie d'énergie, pose une difficulté méthodologique à prendre en compte lors de la conception d'outils d'optimisation d'itinéraires. La récupération se formule majoritairement par des arcs de coûts négatifs, excluant ainsi les méthodes classique de résolution du plus court chemin basées sur l'algorithme de Dijkstra.

This paper applies the theory of Hamilton–Jacobi partial differential equations to the case of first-order traffic flow models. The traffic flow surface is analyzed with respect to the three 2-dimensional coordinate systems arising in the space of vehicle number, time and distance. In each case, the solution to the initial and boundary value problems are presented. Explicit solution methods and examples are shown for the triangular flow-density diagram case. This unveils new models and shows how a number of existing models are cast as special cases.

As cooperative systems, a.k.a. connected vehicles, enable the communication and exchange of information between vehicles and infrastructure, it is expected that their communication capabilities can lead to a better active traffic management on urban motorways. In such a context, technological constraints must be the basis for any management strategy. If it has been analytically proven that communication can help stabilize traffic flow at a microscopic level, it is interesting to evaluate realistic communication strategies taking into consideration multiple perturbations such as sensors faults or driver cooperation. In this paper, a three-layer multi-agent framework is used to model and control the homogenization of traffic flow. The physical layer coordinates the vehicles dynamics based on a cooperative car following model. This layer includes cooperation derived from the communication and trust layers that respectively manage information and its reliability. Simulation results highlight the positive impacts of communication and control on traffic flow stability.

As cooperative systems, a.k.a. connected vehicles, enable the communication and exchange of information between vehicles and infrastructure, it is expected that their communication capabilities can lead to a better active traffic management on urban motorways. In such a context, technological constraints must be the basis for any management strategy. If it has been analytically proven that communication can help stabilize traffic flow at a microscopic level, it is interesting to evaluate realistic communication strategies taking into consideration multiple perturbations such as sensors faults or driver cooperation. In this paper, a three-layer multi-agent framework is used to model and control the homogenization of traffic flow. The physical layer coordinates the vehicles dynamics based on a cooperative car following model. This layer includes cooperation derived from the communication and trust layers that respectively manage information and its reliability. Simulation results highlight the positive impacts of communication and control on traffic flow stability.

This paper presents two empirical trajectory data sets focusing on the merging behaviour on a motorway, both in the Netherlands and in France. A careful review of the literature shows that the main theories explaining this behaviour rely on the hypothesis of gap acceptance, i.e. the fact that each driver has a certain threshold value depending on among other things the distance to the end of the acceleration lane, and when the offered gap is larger than this threshold the driver decides to merge. We conducted a detailed comparative analysis of the two data sets examining the main variables identified in our conceptual model of merging behaviour. The contribution of this paper is that the analysis does not only focus on the accepted gaps, but it also takes into account the rejected gaps. The comparison of our observations with the critical gap formula in literature showed that this formula does not take into account the strong probability of rejecting a gap, even larger than the gap finally accepted. Moreover, we created a logistic regression model that predicts the acceptance or rejection of a given gap, depending on the gap value and the speed difference between the merging vehicle and the putative follower. We have shown that two other factors impact the probability of rejecting or accepting a given gap, but these are significant for just one of the data sets: the distance to the end of the acceleration lane and the speed difference between the putative follower and the putative leader. This shows the impact of the local situation on the merging behaviour (e.g. traffic composition, road geometry, and traffic conditions).

The probability hypothesis density (PHD) methodology is widely used by the research community for the purposes of multiple object tracking. This problem consists in the recursive state estimation of several targets by using the information coming from an observation process. The purpose of this paper is to investigate the potential of the PHD filters for real-time traffic state estimation. This investigation is based on a Cell Transmission Model (CTM) coupled with the PHD filter. It brings a novel tool to the state estimation problem and allows to estimate the densities in traffic networks in the presence of measurement origin uncertainty, detection uncertainty and noises. In this work, we compare the PHD filter performance with a particle filter (PF), both taking into account the measurement origin uncertainty and show that they can provide high accuracy in a traffic setting and real-time computational costs. The PHD filtering framework opens new research avenues and has the abilities to solve challenging problems of vehicular networks.

In the past decade many papers focused on describing the vehicular traffic stream of an arterial on an aggregate level. Unfortunately, in this considerable body of research, only a few papers account for bus systems. This paper tries to fill that gap by investigating two potential methods for estimating macroscopic fundamental diagrams of multimodal transport systems of a signalized arterial. The first approach models the motion of buses endogenously by extending the existing estimation method with the moving bottleneck theory; the second approach proposes to incorporate the effects of buses exogenously. The estimated macroscopic fundamental diagrams were then cross compared with results provided by microsimulation software that finely reproduced the traffic stream. Mean speeds of vehicles and buses produced by the different methods were similar and consistent. Finally, results of the three methods were expressed for levels of service and compared with the levels of service of the Highway Capacity Manual 2010.

The paper aims at evaluating how new financial incentives already existing in the field of mobile telecom (incentive package deals), energy (smart grids) or even air transportation (frequent flyers programs) could be reasonably applied to multi modal land transportation in order to achieve sustainable modal shift from car to other means of public transportation.

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, 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 methodologies have to be investigated. In this aim, we propose in this paper the use of Probability Hypothesis Density (PHD). This methodology is intensively studied, developed and improved for the purposes of multiple object tracking and consists in the recursive state estimation of several targets by using the information coming from an observation process. However, some issues need to be studied, especially the clutter (false alarm) intensity. The goal of this paper is to expose the potential of the PHD filters for real-time traffic state estimation and the choice of an appropriate clutter intensity. This investigation is based on a Cell Transmission Model (CTM) coupled with the PHD filter. It brings a novel tool to the state estimation problem and allows one to estimate the densities in traffic networks. In this work, we compare this PHD filter with the particle filter (PF) which has been successfully applied in traffic control and conclude that the PHD filter can be seen as a relevant alternative that opens new research avenues.

Lancé fin 2009 par le ministère de l'Écologie, du Développement Durable, des Transports et du Logement (MEDDTL, aujourd'hui le Ministère de l'Ecologie, du Développement durable et de l'Energie ou MEDDE), et piloté par le Centre scientifique et technique du Bâtiment (CSTB), le projet « Ville Numérique » a réuni 12 équipes de recherche de stature internationale aux compétences uniques, appartenant aux 5 établissements du Réseau scientifique et technique du Ministère du Développement Durable suivants : le Centre Scientifique et Technique du Bâtiment (CSTB), l'École des Ponts ParisTech (ENPC), l'Institut National de l'information Géographique et forestière (IGN), l'Institut français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR) et Météo France. « Ville numérique » avait pour but d'étudier et de développer différents éléments constitutifs d'une plateforme de simulation intégrée de la ville, en fédérant la grande diversité des expertises complémentaires de ces organismes (traitement d'images, traitement géométrique, formats d'échange de données, SIG3D, génération de maillages, calcul scientifique, architecture logicielle, visualisation scientifique). Cette plateforme ayant vocation à devenir un outil d'évaluation environnementale multicritères de projets d'aménagements urbains, le projet visait donc à développer des indicateurs environnementaux fiables et interopérables, à partir de l'étude de phénomènes physiques de la ville tels que le trafic, l'acoustique, l'aéraulique, l'hydrologie, et la météorologie : Consommation énergétique, rejets de gaz à effet de serre, qualité de l'air, mobilité, bruit, flux d'eau et de polluants... Le projet visait en outre à lever les verrous, en particulier techniques, pour la mise en oeuvre de plateformes informatiques permettant l'intégration des différents outils de gestion, de pilotage et de modélisation utilisés par les acteurs des territoires, notamment urbains. Cela implique notamment l'interopérabilité des modèles mathématiques et des outils informatiques, faisant émerger des interfaces concrètes entre partenaires, aussi bien au niveau scientifique que logiciel. Des fonctionnalités de réalité virtuelle sont également mises en oeuvre, afin de de visualiser et intégrer aisément les résultats dans un environnement 3D immersif.

This paper questions the relevance of microscopic traffic models for estimating the impact of traffic strategies on fuel consumption. Urban driving cycles from the ARTEMIS database are simplified into piecewise linear speed profiles to mimic the classical outputs of microscopic traffic flow models. Fuel consumption is estimated for real and simplified trajectories and links between kinematics and the fuel consumption errors are investigated. Simplifying trajectories causes fuel consumption underestimation, from −1.2 to −5.2% on average according to the level of simplification; errors can approach −20% for some cycles. A focus on kinematic phases indicates that the maximum speed reached and the time decelerating are the main influences on fuel consumption. Finally, in the case where maximum speeds are estimated correctly, it is shown that errors committed at each kinematic phase when acceleration distributions are approximated by their mean values, converge towards small errors over complete cycles. A method is developed to quantify and reduce these errors.

International audience

TRB 2012 - Transportation Research Board 91rd Annual Meeting, WASHINGTON D.C, ETATS-UNIS, 22-/01/2012 - 26/01/2012; This paper reports on the results of a web based survey conducted as part of the MULTITUDE project (Methods and tools for supporting the Use caLibration and validaTIon of Traffic simUlation moDEls). The project, being performed in Europe, is attempting to focus and drive forward the issue of 'model validity' and thereby calibration and validation methods and their usage in simulation. As part of this, an assessment of the state-of-the-practice has been performed, examining among other things how models are applied what procedures are used for calibration and what guidelines are followed. The basis for this state-of-the-practice, is a web based survey which ran in the latter quarter of 2010 and obtained 215 responses. The paper details the finding of this survey which, while lengthy, substantiates two clear messages. Firstly, that Calibration, Validation and Sensitivity analysis although now more widespread than was previously thought, are still far from being required procedure, and secondly that while guidelines are increasingly in use, governing for example number of simulation runs, there are still many regions where this does not occur and indeed there is still much reliance on personal experience and habit, especially in situations where network characteristics become large. The results of the survey underpin the need for further focus on the use of models and procedures for calibration and validation, and indicate, more specifically, the areas that MULTITUDE will focus on in the near future.

International audience

International audience; There is a growing interest in the optimization of dietary emulsions for monitoring postprandial lipid metabolism in the frame of preventing metabolic diseases. Using various emulsions, we investigated in a systematic scheme the combination of (i) in vitro gastrointestinal lipolysis and (ii) absorption and metabolism of lipolysis media in Caco-2 cells. Four emulsions based on either milk fat olein (OL) or rapeseed oil (RA) as the dispersed phase and either lecithin (LE) or sodium caseinate (CA) as the emulsifier were tested. After a sequential incubation of these emulsions with gastric and pancreatic enzymes, lipolysis media were incubated with Caco-2 cells, after dilution (1 : 20) to maintain the barrier integrity. Both gastric and duodenal lipolysis levels were similar to values reported in vivo and the rates of lipolysis were higher with LE-stabilized emulsions than with CA-stabilized emulsions (P < 0.05). TAG secretion by Caco-2 cells was found to be higher using (i) duodenal vs. gastric media (P < 0.001) and (ii) emulsions stabilized with CA vs. LE (P < 0.01). Consistently, gene expression of both FABP2 and FATP4 induced by the duodenal media was (i) higher than that with gastric media (P < 0.001) and (ii) faster than that with model mixed micelles. Using gastric media, TAG secretion of Caco-2 cells after 12 h was higher with RA than with OL (P < 0.001). Moreover, the RA-CA emulsion increased the size of secreted lipoprotein particles (514 nm vs. 61 to 130 nm; P < 0.01). In conclusion, it was possible to observe distinct responses in the lipid metabolism of Caco-2 cells incubated with lipolysis media obtained from different dietary emulsions digested by gastrointestinal lipases in vitro.

Dynamic traffic simulation tools are increasingly being used to help traffic managers and urban planners to make decisions. Therefore, simulation tool users require a validated methodology guaranteeing that simulation results can be trusted. This study contributes to the identification and correction of a possible deficiency in detailed calibration and validation of car-following models: the data errors of individual trajectory data. Some studies addressed the problem of filtering trajectory data. A new filtering technique to reduce the measurement errors on trajectories, speed profiles, and acceleration profiles is proposed here. This technique is based on some piecewise polynomials termed “splines.” The proposed technique is compared with a set of filtering techniques found in the literature. A complete trajectory data set available within the NGSIM program is used. As a quality indicator of the various filtering techniques, velocity distribution, acceleration distribution, and jerk analysis are used for the whole data set. Also, analyzing acceleration standard deviations for each trajectory of the data set is suggested. The main findings are as follows: (a) of the methods compared within this work, the I-spline method with the action points most reduces the spikes in the velocity distribution; (b) moreover, the I-spline method most reduces the percentage of jerk values higher than 15 m/s3 as well as the percentage of the 1-s windows with more than one sign inversion of the jerk; and (c) in some cases, this method increases the acceleration variability of smoothed trajectories.

TRB 2009 - Transportation Research Board 88th Annual Meeting, WASHINGTON D.C, ETATS-UNIS, 08-/01/2009 - 11/01/2009; This paper is concerned with the impacts of lane-changing maneuvers in traffic streams. A new methodology is developed based on the simplified kinematic-wave theory and only requires one assumption: a constant speed of the backward-moving characteristic along a large platoon of vehicles. This method consists in quantifying the net impact of entering and exiting-lane changing maneuvers among a platoon of fifteen vehicles. It has been applied to two highway trajectory datasets from the NGSIM program. Findings from this study show that the impact of lane-changing depends on the net number of entering vehicles to a lane, and insertions have greater impacts in traffic stream than exits.

The objective of this paper is to prove the effectiveness of variable message sign information on recurrent congestion using different measurements of effectiveness. To show the benefits of the information systems, we have built a new methodology. We took advantage of the data collected during a national strike which shut down the variable message signs. By comparing these data to a set of 'normal' days we can evaluate the impact of information systems on congestion level. We present a way to measure the effectiveness of information systems. For the evaluation of information effectiveness we use both qualitative and quantitative measurements. This allows us to finally give a financial assessment of information systems for commuters. Our study is based on an 80 km long suburban network in Lyon. We show that the benefits of an information system can be evaluated between 0.7 and 1 M per year (between 0.9 and 1.3 M US $ per year).

Bi-modal or 3D-MFD relates the accumulation of cars, buses to total production at the network level. The current work provides a detailed discussion of extended MFD-based models namely, accumulation-based and trip-based models that accounts for bi-modal flows through 3DMFD. In addition, delay accumulation-based models, also known as exit-flow models in classical traffic flow theory, are revisited. Fundamental modeling differences between different MFDbased models are illustrated using a benchmark test case. A new FIFO-based entry flow function is also proposed in order to address the inconsistencies of the conventional entry flow function in the context of the 3D-MFD case. A novel weak internal FIFO discipline is proposed to circumnavigate the violation of internal FIFO order during network unloading in the delay accumulation based model. MFD-based models are verified using the solutions of micro-simulations performed on an idealized grid network. The importance of separating the 3D-MFD into partial car and bus 3D-MFDs is highlighted. Moreover, it is also shown that partial bus 3D-MFD should be further split when dedicated bus lanes are present in the network to account for unequal mean speeds between different bus lanes.

This paper describes how dynamic lane allocation strategies may improve bus transit. The considered strategies are bus lanes with intermittent priorities (BLIPs). These strategies consist in intermittently opening the bus lane to general traffic when not in use by a bus. Even if benefits of such strategies have been pointed out in the literature, the activation process has received little attention. Chiabaut et al. (2012) has firstly proposed an analytical approach for BLIPs activation. However, the analytical (extended) kinematic wave model uses a rough description of lane-changing maneuvers. This paper tries to overcome this limitation through a refined approach using the simulation package SymuVia. The simulated results show a good agreement with analytical results. For comparable case, simulation enables more sophisticated case to be investigated. A sensitivity analysis is carried out to identify the parameters that have the most influence on BLIPs activation efficiency.

In recent years, several perimeter control strategies have been proposed for traffic management in cities. The common factor found in these works is the use of Macroscopic Fundamental Diagram (MFD) models to describe the dynamics of the network and optimize traffic inside the perimeter by manipulating perimeter inflows. Perimeter gating control strategies are attractive for traffic management inside the inner city. However, it inevitably creates a negative impact on the traffic outside. Most of the works in this research area have neglected vehicle re-routing outside the controlled perimeter, i.e., they do not consider demand elasticity to the central region resulting from gating and the related queues. In this paper, we propose a global modeling framework capable of assessing the effect of perimeter gating control (in terms of queue, emission, and total time spent) on the full network, considering demand elasticity resulting from Dynamic User Equilibrium (DUE). Classical Proportional-Integral (PI) control scheme is used to control traffic congestion inside a central region (reservoir). The modeling framework is comprised of: (i) an accumulation-based MFD model to reproduce traffic dynamics inside the reservoir, (ii) point-queue model to represent queuing vehicles on inbound links to the gating points, and (iii) a time-dependent travel time profile based on a steady-state approximation of MFD dynamics to characterize the alternative road network (bypass). DUE is then implemented, considering instantaneous predicted travel time. This determines how the demand to the inner region is affected by the gating. The functioning of the global system is assessed by total time spent and NOx and CO2 emissions inside the reservoir and for the full network. The presented simulation results show that the perimeter gating control helps to maintain congestion at the desired level with significant improvements in the total time spent and the mean speed in the network. However, it shows a slight increase in the queues. As expected, deviation to the bypass alternative is significant and should not be neglected when carrying out a global assessment of gating system performance.

Shared mobility services have been hailed as a game changer in transportation and a promising solution to reduce congestion and improve urban mobility. However, only a few studies have attempted to determine if significant demand for such services really exists. This article marks a first attempt toward this objective by employing ridesourcing trip data to identify twin travelers. Using the DiDi Chuxing dataset, a general methodology is defined to assess the similarity between trips and to cluster comparable travelers. The study reveals, among other things, that at least 18% of trips can be paired without introducing significant delays.

Congestion in urban areas has become a major issue in terms of economic, social or environmental impact. For short or mid term, using dynamic road traffic simulation can help analyzing and providing guidelines to optimization policies of existing infrastructures. Today, because of the complexity of transport systems, classical modeling tools are limited to small geographical areas (of a district size). Computational time, together with simulation calibration, are notably very constraining at large scales. However, a new generation of models designed for metropolitan areas has arisen over the past decades. These models are based on a phenomenological relationship between travel production and the number of vehicles in a given spatial area of a road network, known as the Macroscopic Fundamental Diagram (MFD). This relationship, supported by empirical evidences from several cities around the world, has allowed the study of different traffic control schemes at a whole city scale, but was rarely used for traffic state forecasting. The aim of this PhD is to propose an efficient modeling tool, based upon the concept of MFD, to simulate and analyze traffic states in large metropolitan areas. The theoretical framework of this tool must be consistent and applicable for traffic state forecasting, development of new control policies, traffic emission estimation, etc. There are two major contributions in this PhD. The first one is analyzing the mathematical and physical properties of existing models, and formalizing the dynamics of several trip lengths inside the same urban zone. In particular, this formalization distinguishes between internal trips and trips crossing the zone. Flow merging and diverging issues are also addressed when congestion propagates from one zone to another. The second contribution is proposing a new trip-based model based on individual traveled distance. This approach allows to treat users independently (previously represented with continuous flows), and thus to define their characteristics more precisely to couple their trips with assignment models on different paths. Finally, examples of application from various collaborations are given in the last part of this thesis. It includes a simulation study of the Grand Lyon urban area (France), as well as new modules to simulate search-for-parking or perimeter control. This PhD is part of a European ERC project entitled MAGnUM: Multiscale and Multimodal Traffic Modeling Approach for Sustainable Management of Urban Mobility.; La congestion en milieu urbain est un enjeu majeur que ce soit d’un point vue économique, social ou environnemental. À court et moyen terme, l’utilisation de la simulation dynamique du trafic routier peut permettre d’analyser et de guider des politiques d’optimisation des infrastructures existantes. Aujourd’hui, du fait de la complexité des systèmes de transport, les outils de modélisation classiques sont limités à des échelles géographiques peu étendues (de l’ordre du quartier). À grande échelle, le temps de calcul devient rapidement un facteur limitant tout comme le calibrage et la scénarisation. Néanmoins les dernières décennies ont vu l’apparition d’une nouvelle génération de modèles bien adaptés aux métropoles urbaines. Ceux-ci sont basés sur une relation phénoménologique entre la production de déplacements et le nombre de véhicules dans une zone spatiale d’un réseau routier, appelée Diagramme Fondamental de Zone (Macroscopic Fundamental Diagram, MFD). Cette relation, validée empiriquement sur de nombreuses villes, a permis d’étudier différentes méthodes de contrôle du trafic pour une ville entière, mais a été peu utilisée à des fins de prévision de la congestion. L’objectif de cette thèse est de proposer un premier outil opérationnel de simulation et d’analyse des grands réseaux de métropoles, en utilisant et développant les modèles de trafic basés sur la relation MFD. Cet outil doit posséder un cadre théorique cohérent qui puisse convenir à des applications telles que la prévision d’états de trafic, le développement de nouvelles politiques de contrôle, l’estimation de pollutions liées au trafic, etc. Les contributions de la thèse portent sur deux aspects. Le premier est l’analyse des propriétés mathématiques et physiques des modèles existants, en incluant une formalisation complète de la gestion de plusieurs longueurs de parcours au sein d’une même zone urbaine. En particulier, cette formalisation traite de la distinction des trajets internes à la zone et des problèmes de flux convergents et divergents pour les trajets traversant la zone lorsque la congestion se propage d’une zone à l’autre. Le deuxième aspect est la proposition d’un nouveau modèle basé sur la distance individuelle parcourue à l’intérieur d’une zone urbaine (trip-based). Cette approche permet d’individualiser les usagers (auparavant représentés sous forme de flux continus) et donc de définir plus finement leurs caractéristiques, en vue de coupler leurs déplacements à des modèles d’affectations sur différentes routes. Enfin, des exemples d’application illustrant diverses collaborations sont donnés en dernière partie de la thèse. La simulation du trafic sur l’aire urbaine du Grand Lyon (France) y est présentée, ainsi que de nouveaux modules de modélisation de la recherche de parking ou de contrôle périphérique. Cette thèse est partie intégrante d’un projet européen ERC intitulé MAGnUM : Approche multi-échelle et multimodale de la modélisation du trafic pour une gestion durable de la mobilité urbaine.

hEART 2018, 7th Symposium of the European Association for Research in Transportation, Athènes, GRECE, 05-/09/2018 - 07/09/2018; Unicity of the solution is an important issue in the Dynamic Traffic Assignment (DTA) problem (Beckmann et al. (1956)). The conditions of unicity have been properly reviewed by Iryo (2013) for flow-based DTA by considering the different approach to solving the DTA problem. Moreover, many researches have been done to prove the unicity of DTA solutions on flow-based dynamic traffic model with several assumptions and limitations on traffic network model (Mounce (2007); Mounce & Smith (2007); Iryo (2011); Iryo (2015); Iryo & Smith (2017)). This study adapts the conditions to trip-based DTA wherein each traveler is defined as an individual.

The purpose of this study is to compare network loadings related to different network equilibria by a simulation-based framework. The direct comparison of path flows or trajectory patterns is hard to achieve so here we propose a more aggregate approach based on the comparison of demand level breakpoints. A breakpoint is a demand threshold value that leads to significant changes in path flow loading. More specifically, we set in this paper a demand breakpoint when the list of effective route alternatives differs by at least one path. This is for example the case when one route is no longer considered for one equilibrium while being used by some vehicles in the second one. We are going to investigate both static and dynamic network loading while scanning all demand levels to identify the breakpoints. We focus on discrete demand formulation and choices and use a trip-based traffic simulator. This study analyzes the breakpoints for the solution of three popular equilibrium conditions: User equilibrium (UE), System optimum (SO) and Boundary Rational User Equilibrium (BRUE). First, we investigate breakpoints on a well-known network (Braess) in the static case in order to better define this concept. Second, breakpoints are investigated on a real network (Lyon, France) where dynamic travel times are provided by a microscopic traffic simulator. When the breakpoints are obtained for a given scenario, we focus on identifying demand ranges where some paths are not used in SO while being travelled in UE or BRUE. Following the concept of Braess paradox, this permits to design banning strategies at some key locations in the network to prevent some alternatives from being used and thus to improve the system performance. We show by simulation that such a strategy is effective, which demonstrates the importance of breakpoint identification.

The concept of the Macroscopic Fundamental Diagram (MFD) is elegant and attractive because it provides a global view of traffic behavior and performance at a network level. However, recent research shows that the MFD shape can be influenced by local traffic heterogeneities. Notably, route choices and heterogeneous local capacities may drive uneven (in space) or inconsistent (in time) distributions of congestion and then affect the shape and the scatter of the MFD. We are far from having a global understanding of the connections between local phenomena and the resulting MFD. This paper first aims to improve existing MFD estimation method for a succession of links with traffic signals. The new method overcomes previous limitations, notably regarding to the topology and signal settings regularities, by fully utilizing the receipts of the variational theory. Then, a single network with several parallel routes is investigated. MFDs on different routes are estimated with the variational method and then aggregated in a unified MFD for stationary and dynamic conditions and different sorts of equilibria (user and system optimum). It appears that the flow distribution among routes smoothly varies with respect to the total flow either in free-flow or congestion situations. Such a distribution is much more rough for system optimum, where it presents some discontinuities and is far from equity. This means that a control strategy able to lead such a network to the perfect system optimum would be hard to tune, especially in the congested regime. However, being able to determine the MFD corresponding to the system optimum provides a valuable reference to estimate the current efficiency of the considered network. Case studies for different simple networks and insights for generalization at the city level are proposed. (C) 2013 Elsevier Ltd. All rights reserved.