On the Marginal Cost of Road Congestion: an Evaluation Method with Application to the Paris Region

The paper analyzes the sensitivity of the marginal congestion cost on a roadway network to the level of aggregation in space, from utmost disaggregate to utmost aggregate. Simulation and aggregation are based on a static network assignment model.Marginal cost ; Road congestion ; Cost aggregation ; Congestion indicator ; Assignment model

The Theory and Practice of a Dual Criteria Assignment Model with a continuously distributed Value-of-Time

24 pagesInternational audienceA dual criteria assignment model enables an analyst to represent disaggregate trade-offs between two cost criteria in the trip-makers' route choices, e.g. time and price in the cost vs. time model in which a continuously distributed value-of-time (VOT) is assumed. This paper develops the theory and practice of dual criteria assignment. First, the economic background of the model is set out: it enables the analyst to represent various route choice behaviors, variable demand, several user classes, flow-dependent travel time and capacity constraints. Second, the mathematical framework is introduced; due to a special transformation, the model is cast into a variational inequality which under some assumptions reduces to a convex minimisation program. Third, solution algorithms are introduced and compared. Fourth, econometric tools are provided to estimate the distribution of the VOT and to evaluate the uncertainty about the predicted revenue of a toll road, arising from the uncertainty about the distribution of the VOT. It is shown that these tools ensure the practicality of a dual criteria assignment in a medium-sized application

Modelling a vehicle-sharing station as a dual waiting system: stochastic framework and stationary analysis

19 pagesA waiting system with two kinds of resources, say the vehicles and the docks in a vehicle-sharing service, is considered. Two arrival flows of customers are assumed, access customers who require a vehicle versus egress customers that bring back their vehicle and require a dock at the station. The total number of docks sets a limit capacity for the service. A stochastic, markovian, state-transition model is defined, which constitutes a bi-sided capacitated queuing system. The balance equations are stated and solved, yielding a stationary distribution under two conditions of compatibility. Indicators of service quality and system performance are defined and formulated under steady state

On Seat Congestion, Passenger Comfort and Route Choice in Urban Transit: a Network Equilibrium Assignment Model with Application to Paris

16 pagesInternational audienceIn network assignment models of urban transit, traffic congestion has been modelled either as vehicle congestion along the route track, or by reducing the service frequency with respect to excess flow of passenger arrivals. A third type of congestion has been modelled by Leurent (1), (2): that of seat congestion, because being seated or standing make distinct on-board states for a transit rider, resulting in distinct discomfort costs, with potential influence on route choice on the transit network. The paper has a twofold objective of, first, providing a concise statement of the seat congestion model, and second, reporting on its application to the Paris metropolitan area – a problem of very large size. The model makes explicit the residual set capacity and its evolution at any stage along a service line; the priority rules amongst riders depending on their order of arrival in the competition to get a seat; and the randomness in leg cost to the rider. Line algorithms and consistent network algorithms are provided

On modal availability, travel strategies and traffic equilibrium on a multimodal network

27 pagesTransportation modes, including Walking and other private modes as well as transit services, provide travel options to the individual trip-maker along a transportation network. On a single basis, any modal option is featured here in terms of travel time to destination conditionally to immediate availability, expected wait time in the adverse case and the probability of availability. The paper is focused on availability in order to state its roles in travel strategy for route choice and traffic assignment onto a multimodal network. It deals with, successively, mode characterization, local travel strategy, network hyperpaths and traffic equilibrium. Assumedly, a private mode is available on a full, continuous basis, while a transit service is available on a partial, discrete basis due to station dwell time and service frequency. However, a capacitated transit service under saturation amounts to a fully available travel option which includes an initial wait time. A local travel strategy at a choice node is made up of either an ordered sequence of discrete options, or a continuous option, or a combination of both so that the discrete options are used opportunistically if available or the continuous one otherwise. This leads us to revisit the common line problem of transit assignment. A framework and an algorithm are provided to search for optimal travel strategies. The sequential treatment along a multimodal network is based on hyperpaths under availability conditions. Traffic equilibrium is addressed in the static setting; the system state includes the vector of trip flows by destination and network link together with vectors of strategy proportions by node and destination

Modelling seat congestion in transit assignment

Submitted to Transportation Research Part B, manuscript TRB-D-08-00194 27 pagesSeating or standing make distinct on-board states for a transit rider, resulting in distinct discomfort costs, with potential influence on route choice on the transit network. The paper provides a model for seat congestion: from assumptions on seat capacity, travel behaviour and priority rules, a seat allocation process is described, resulting in the notion of service modes for a transit leg, making the leg cost a random variable. At the line level, line algorithms for flow loading and leg costing are provided, which are efficient. At the network level, a hyperpath formulation is provided for supply-demand equilibrium, with path-dependent segment cost, assignment algorithm and a property of existence. It is shown that multiple equilibria may arise. Model extensions by adding discomfort functions, taste differentiation, or discrete choice to compete or not for getting a seat, might induce uniqueness

Curbing the computational difficulty of the logit equilibrium assignment model

26 pagesInternational audienceIn the past, research in traffic assignment modeling has been directed primarily towards improving the deterministic model. Alternative, more behavioral principles were thought to be too demanding computationally. This paper presents two mathematical contributions that enable one to solve a logit assignment model with flow-dependent travel times at a reduced cost. First, a convergence test for Fisk's minimization program is introduced, based on a duality gap principle. Second, a new definition of Dial's STOCH fixed-time logit assignment procedure is given, in which the set of available paths is defined only once and the computations are re-interpreted. A numerical experiment indicates that these tools make the logit assignment model very competitive compared to the procedures conventionally used for solving the deterministic model

Contributions to the logit assignment model

16 pagesInternational audienceIn the past, research in traffic assignment modeling has been directed primarily towards the deterministic model. Alternative, more behavioral principles were thought to be too demanding computationally. This paper presents two mathematical contributions that enable one to solve a logit assignment model with flow-dependent travel times at a reduced cost. First, a convergence test for Fisk's minimization program is introduced, based on a duality gap principle. Second, a new definition of Dial's STOCH fixed-time logit assignment procedure is given, in which the set of available paths is defined only once and the computations are re-interpreted. A numerical experiment indicates that these tools make the logit assignment model very competitive compared to the procedures conventionally used to solve the deterministic model

Sensitivity and error analysis of the dual criteria traffic assignment model

International audienceIn the dual criteria traffic assignment model, to take into account various trade-offs between travel time and travel cost, the value of time is assumed to be continuously distributed across the trip-makers. This paper presents a sensitivity and error analysis method for the equilibrium solution of a dual criteria model with elastic demand, flow-dependent travel times and side constraints. The method is based on previous work by Tobin and Friesz (1988) to bypass the uniqueness requirement in standard sensitivity analysis frameworks for variational inequalities, and exploits the finite-dimensional formulation of the model in terms of path flow variables given by Leurent (1996a). The paper contains three parts. The first demonstrates the usefulness of sensitivity analysis using a two-link network. The second addresses the general network case. Lastly, the third presents an application to a realistic traffic study

Les entreprises françaises face à l'automobilité et à la mobilité électrique : enjeux, mécanismes de décision et perspectives d'évolution

National audienceDes véhicules électriques à l'autonomie accrue et au prix allégé sont désormais proposés par plusieurs constructeurs automobiles. Certains opérateurs de mobilité les ont intégrés déjà afin d'innover dans l'offre de services : cf. notamment le projet Autolib à Paris et divers équivalents dans d'autres villes. Cependant, au-delà des flottes de véhicules en libre-service, l'adoption d'une voiture électrique en tant que voiture particulière par un ménage ou par une entreprise reste problématique, car l'autonomie reste largement en-deçà de celle des voitures thermiques, et ce à un prix légèrement supérieur pour des parcours annuels moyens, selon les conditions économiques en vigueur en France en 2012. Les entreprises, dans leur dimension d'usagères de produits et services automobiles, peuvent constituer des cibles privilégiées, et ce pour plusieurs raisons. Si dans la mobilité des voyageurs, les motifs professionnels ne comptent que pour un dixième environ des déplacements et des parcours réalisés, en revanche les entreprises constituent un segment majeur pour l'achat des véhicules neufs : 42% des voitures achetées neuves sur le marché français en 2011. De plus, l'entreprise est par essence et par excellence le lieu de décisions économiques rationalisées, basées sur des outils de gestion : s'il existe des niches d'efficacité pour la voiture électrique, l'entreprise est bien placée pour les détecter et en tirer profit. Enfin, l'entreprise sait gérer le facteur temps mieux que les particuliers : elle sait choisir un investissement au prix initial supérieur du moment que l'usage anticipé s'annonce plus économique en retour. La communication traite des méthodes de gestion de la mobilité en entreprise, et rapporte une enquête de terrain réalisée auprès d'un échantillon de gestionnaires, afin de diagnostiquer la situation stratégique des entreprises face à la mobilité, et de pronostiquer le potentiel de la voiture électrique sur ce segment de marché. L'enquête tient une place essentielle, car il n'y a quasiment pas de littérature académique sur le sujet ; celui-ci fait l'objet d'une attention soutenue dans la presse professionnelle spécialisée, mais avec des argumentaires en général incomplets et parfois inexacts. De fait les pratiques professionnelles méritent certainement d'être revisitées, rationalisées et reconçues, ne serait-ce que pour les décliner en fonction de la nature d'activité et du territoire d'exercice. Après une introduction qui rappelle les conditions de pertinence du véhicule électrique face au véhicule thermique, la communication présente une analyse a priori de la gestion de la mobilité en entreprise. Puis elle décrit les principes et la méthode de l'enquête auprès des décideurs. Ensuite elle en synthétise les résultats, et finalement elle les " discute en prospective "