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We contribute to the vehicle-level analysis of two macroscopic features of the road traffic: capacity variability and capacity drop. In this paper, we focus only on the car-following behavior and leave the part related to lane-change maneuvers for the future research. In particular, we study a simplistic car-following model (Newell's with bounded acceleration) for a single-lane scenario. In this work, by introducing a speed limitation across a zone, a bottleneck with variable nominal capacity has been created. We use a continuous event-based numerical resolution method. Consequently, We are able to vary the three Newell's model parameters: maximal acceleration, minimal distance, reaction time. It has been shown that the variability of those car-following parameters (e.g., reaction-time, minimal-distance, and maximal-acceleration) has a strong impact on the pre-breakdown capacity variation and also on the queue discharge flow. It has been concluded that this parameters variability does impact the drop (provided that the maximal acceleration has a relatively high mean value). Various distribution shapes (uniform, truncated Gaussian, and Gamma) have been exploblack. It has been realized that this does not have any significant impact on the capacity distribution. Concerning the amplitude of the capacity distribution, we demonstrate that the reaction time is the parameter with the highest impact followed by the minimal distance. If all parameters vary with an amplitude of 30 \%, we show that the capacity standard deviation, in this scenario without lane changes, is about half the experimental values reported in the literature.

4th webinar Ectri Traffic Management Thematic Group, Bron, FRANCE, 08-/10/2020 - 08/10/2020; We realized an analysis of the CACC data of the Volpe laboratory. We observe that the response times distributions are spreading when the distance to the leader and the position in the platoon increase. This leads us to question the connectivity inside those platoons.

International audience

This text is the result of the Thematic Group Traffic Management of the ECTRI – European Conference of Transport Research Institutes. As a position paper, it states the challenges that the European Research Agenda will have to face if the following goals for a future transportation system are considered: • User-aware mobility • Zero accidents and zero emissions • Minimum space, time, energy & costs for transport It describes in a concise manner the research approaches needed to achieve the realization of these goals.

Les temps de stationnement en gare en Île-de-France peuvent avoir un impact significatif sur la régularité des trains transilien. L'optimisation des durées de stationnement est essentielle pour une exploitation efficace, en n'étant ni trop courtes, ni trop longues. Le déploiement d'un système de comptage automatique des voyageurs embarqué permet de comprendre les déterminants d'une telle durée optimale. Il en résulte une modélisation du temps de stationnement minimal, effectuée par gare et par sens, qui permet d'évaluer la probabilité que les temps de stationnement prévus dans la grille horaire soient respectés ou soient source de retards.

The stakes that were targeted by this collaboration are linked to the rarefaction of resources used to build new transportation infrastructures and to the higher attention paid to the environmental impacts of mobilities. Indeed, transportation network managers have a real need for tools and methods to master the increase of movement demand while reducing the impacts of these moves. On these topics, the research done in the Ifsttar allied to the expertise of the Cerema gave birth to a form of integrative research that contributed to broaden the horizons of both partners. The main results of this collaboration are presented in this final report. They comprise: •Better understanding of flows propagation inside the transportation system;•Quantification tools for assessing the impacts of this flow in terms of travel time and accessibility as well as pollutants levels;•Offer of new simulation and modelling tools, that can be used in more situations; (because their calculation time is smaller and they include the effects of regulations);•Strengthening of the methodologies to assess the regulation of suburban motorways. In addition to the presentation of those results, the report includes a list of the productions of the collaboration, the most significant productions, the presentations made during the final seminar and directions for future research.; Les enjeux que cette collaboration a permis de traiter sont liés à la raréfaction des ressources permettant de construire des nouvelles infrastructures de transports et à la montée de la prise en compte des impacts environnementaux des mobilités. Ceci génère un réel besoin, de la part des gestionnaires de réseaux de transports, d’outils et de méthodes leur permettant de maîtriser la croissance de la demande de déplacements tout en diminuant les impacts de ces déplacements. Sur ces sujets, l’articulation des recherches conduites à l’IFSTTAR et de l’expertise que possède le CEREMA a donné lieu à une recherche intégrative qui a contribué à élargir les horizons de chacun des deux partenaires. Les principaux résultats de Messigéo, présentés dans ce rapport final, concernent : •Amélioration de la compréhension de la propagation des flux dans le système de transport ;•Quantification des impacts du fonctionnement du système de transports en termes de temps de parcours et d’accessibilité, tout comme sur les niveaux de polluants ;•Proposition de nouveaux outils de modélisation et de simulation, utilisables dans plus de cas (car ils sont de temps de calcul faible et qu’ils intègrent les effets des régulations) ;•Consolidation des méthodologies d’évaluation des régulations des autoroutes périurbaines.Outre une synthèse de ces résultats, ce rapport contient également la liste des publications, les productions les plus significatives, les présentations faites au cours du séminaire de restitution, et des pistes de recherche future.

International audience; L'émergence de nouveaux modes de collecte de données sur les déplacements est une des conséquences de la massification des "smart phones". Ceci crée une nouvelle chaîne de production d'information routière. Sa collecte et sa diffusion gratuite à l'usager assurées historiquement par l'exploitant cohabitent maintenant avec une information devenue un produit d'appel. Un produit comme un autre ?

Présenté par Christine Buisson lors de la conférence; International audience

TRB 2018, 97th Annual Meeting Transportation Research Board, Washington, ETATS-UNIS, 07-/01/2018 - 11/01/2018; This paper sheds some light on the macroscopic and microscopic characteristic of traffic flow on freeways in the merging areas in presence of Human-Driven Vehicles (HDV) and Connected Autonomous Vehicle (CAV) by thoroughly digging into the literature, exploiting real data and simulating simple scenarios. In particular, in the first step, an extensive literature review on merging behaviour for current and future traffic conditions (i.e. having HDV or HDV and/or CAV on the road) has been carried out. This is followed by an analysis of single vehicle data from a freeway in Lyon to illustrate current speed and headway distributions which are most likely to change with the introduction of CAV's. Finally, some microscopic simulation results are presented which show that traffic flow typically gains from the introduction of CAV's, but may also display negative consequences under certain circumstances. This simulation study focused mainly on the traffic characteristics at the merging area in presence of CAV. It remains for future work to map out precisely where the introduction of CAV's improves the traffic system, and where amendments have to be made to prevent negative side-effects. It should be noted that calibrating and validating the micro-simulation tools which simulate traffic scenarios in presence of CAV's will indeed be challenging in the future. This needs extra attention for research.

TRB 2016, Transportation Research Board 95th annual meeting, WASHINGTON D.C, ETATS-UNIS, 10-/01/2016 - 14/01/2016; This text looks at calibration and validation as a means to understand traffic flow models better. It concentrates on the car-following part of it and demonstrates that the calibration of stochastic models under certain circumstances can become very difficult. Three types of stochasticity are distinguished for microscopic traffic flow models: the one coming from noisy data, the one coming from the distribution of the parameters describing the driver's behavior and the one coming from the model itself, when a noise component is added to a deterministic differential equation governing the vehicle's movements. By using four sub models comprising four different noise terms and an identical deterministic part this text shows that a calibration with synthetic - and therefore reproducible - data can lead to awry results. Parameters fitted by the calibration procedure are significantly different for deterministic and stochastic models. The text makes the conclusion that the stochasticity is the reason why the parameter estimation of stochastic models fails sometimes. Up to now, the authors were, unfortunately, not able to propose a solution to cope with this intrinsic pitfall of genuine stochastic models.

TRB 2016, Transportation Research Board 95th annual meeting, WASHINGTON D.C, ETATS-UNIS, 10-/01/2016 - 14/01/2016; Lane changes are an important aspect of freeway flow. Most lane change models are microscopic, describing whether individual vehicles/drives will change lanes, and hence are calibrated microscopically. Macroscopic validation often is restricted to the distribution of vehicles across lanes. To the best of our knowledge, no systematic analysis has been made of the number of lane changes as function of the operational characteristics of the origin and target lane. This paper fills that gap, by analyzing the number of lane changes as function of several incentives. Based on data availability, two 'simple' sites are selected, i.e. as close as possible to a straight continuous freeway. Statistically, we find that on the selected sites, drivers change lanes on average once per two kilometer driven. Furthermore, analyzing the number of lane changes (per kilometer per hour) as function of the density in the origin lane and in the target lane, we find, as expected, this increases with the density in the origin lane for a fixed density in the target lane. Surprisingly, it also increases with the density in the target lane for a fixed density in the origin lane. The underlying mechanism is therefore different than gap acceptance theory. The analyses presented in this paper can be used to qualitatively verify (microscopic and macroscopic) lane change models, and to propose better lane change models.

TRB 2016, Transportation Research Board 95th annual meeting, WASHINGTON D.C, ETATS-UNIS, 10-/01/2016 - 14/01/2016; Filtering methods for the position or the speed measurements of the NGSim trajectories dataset are numerous, but specific to the noise resulting of NGSim data collection and processing. The MOCoPo (Measuring and mOdelling COngestion and POllution) collaboration collected more than 10 hours of data with a high resolution camera mounted underneath a helicopter flying almost immobile above a freeway in Grenoble. Along with the post-treatment method, this generates a noise in the position measurement of the center of gravity of the image associated with the vehicle. We present a method classically based on polynomial fitting but where the originality states in using the polar coordinates instead of the Cartesian ones as is usually done. Indeed the radial coordinate capture most of the physics of the act of driving a car: selecting a speed, whereas the polar angle is much more related to the geometry of the road. The method fits the space travelled whose derivative is the real instantaneous speed. This method is developed in two versions: piece-wise constant accelerations or piece-wise linear accelerations. In both cases the root mean square error of the position measurements is of less than 0.4 m. The main advantage of this method is that it provides values of acceleration fully compatible with the physical limits found in the literature, without adding extra constraint.

The objective of this paper is to propose an analytical traffic model adapted to freeway weaving sections. To this aim, a theoretical weaving section is considered at the macroscopic level as the superposition of two merges and two diverges. The model endogenously incorporates the capacity drop related to the weaving lane changes. It only depends on six parameters: three parameters of the fundamental diagram (the free-flow speed, the jam density and the wave speed in congestion), the vehicles' acceleration, the relaxation factor and the length of the anticipation zone. A sensitivity analysis proves that the acceleration rate and the relaxation parameter most influence the capacity drop. The analytical model agrees well with microsimulation results and empirical data collected on a weaving section in France.

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.

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.

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.

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., JRC.F.8-Sustainable Transport

The high level of traffic demand, the significant number of players involved and the close-knit relationships between road networks make road traffic a complex area to study. Network congestion is an increasingly common phenomenon that is directly perceived by the general public, insofar as many users have personal experience of it. This explains why traffic theoreticians have been trying to gain a better, quantified understanding of the mechanisms in operation for the past 50 years or so. This publication aims to provide an accessible review of the subject at this point. Firstly, it sets out the different variables used to characterise the progress of vehicles along a thoroughfare, and secondly the fundamental relationships between some of these variables. By way of illustration, this is followed by a number of simple calculations for estimating the time taken to get through a traffic jam. The next section looks at the concepts of cumulative flows and journey times, whilst the last chapter deals with the problem of interconnected networks and calculations relating to spatio-temporal changes in congestion. Finally, there are a number of appendices, with a series of exercises and suggested answers, a French-English glossary and a bibliography. This publication is aimed primarily at professionals dealing with the problems of congestion, whether as operators of urban, suburban or interurban transport networks, or heading up research into the design of new infrastructure or improving the operation of existing infrastructure. It may also be of interest to undergraduate and Masters students, particularly those studying engineering., Le niveau éleÎ de la demande de trafic, le nombre important d'acteurs concernés, ainsi que le maillage des réseaux viaires, contribuent à faire du trafic routier un domaine d'études complexe. La congestion des réseaux est un phénomène de plus en plus courant, et directement perceptible par le grand public, car elle est subie par de nombreux usagers. C'est pourquoi, depuis une cinquantaine d'années, des théoriciens du trafic cherchent à mieux comprendre et à quantifier les mécanismes à l'oeuvre. Le présent ouvrage tente de faire le point, de manière accessible, sur le sujet. Il présente en premier lieu les différentes variables qui permettent de caractériser la progression des Îhicules sur une voie, puis la relation fondamentale qui permet de relier certaines de ces variables. À titre d'illustration, quelques calculs simples, permettant d'estimer le temps de traversée d'un bouchon, sont ensuite fournis. Les notions de débits cumulés et de temps de parcours sont ensuite abordées. La problématique des réseaux maillés, ainsi que les calculs d'évolution spatio-temporelle de la congestion terminent l'ouvrage, qui est par ailleurs complété par plusieurs annexes (série d'exercices avec leurs corrigés, glossaire français -anglais et bibliographie).

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.

TFT Summer meeting Greenshields, Woods Hole, ETATS-UNIS, 08-/07/2008 - 10/08/2008; New Insights on congested part of the FD calibration from Loop Detector Data

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).