Dynamic Trip Assignment-Simulation Model for Intermodal Transportation Networks Khaled F. Abdelghany and Hani S. Mahmassani Department of Civil Engineering, ECJ 6.2, University of Texas at Austin, Austin, TX 78751. software. However, the intermodal framework is not limited to this particular simulation-assignment tool and could be implemented with alternative platforms. The new model approach considers intermodal transportation networks consisting of different travel modes such as private cars, buses, metro-subway, and high-occupancy vehicles (HOVs). The model captures the interaction between mode choice and traffic assignment under different traveler information provision strategies. It implements a multiobjective assignment procedure in which travelers choose their modes and routes based on a range of choice criteria. The model assumes a stochastically diverse set of trav- elers in terms of underlying preferences (relevant choice criteria and associated trade-off rules) as well as in terms of access and response to the supplied information. The modeling tool is intended primarily for operational planning applications, and it could also be used in con- junction with real-time traffic management systems. As a within-day dynamic assignment procedure, it overcomes many of the known lim- itations of static tools used in current practice. These limitations relate to the types of alternative measures that may be analyzed and to the policy questions planning agencies are increasingly asked to address. A review of mode-route choice modeling is presented in the next section. The conceptual framework and structure of the model are then presented, followed by a description of the vehicle simulation components, especially those pertaining to the newly implemented transit and intermodal elements. Two sections present the assign- ment components of the model, which include the multiobjective shortest path algorithm and the mode-route choice procedures. A set of simulation experiments designed to illustrate the capabilities of the model are presented, followed by discussion of the results. Conclud- ing comments and areas for future research are outlined in the final section. MODE-ROUTE CHOICE DYNAMICS IN INTERMODAL NETWORKS Several approaches have been proposed over the past two decades to model and analyze transportation networks with several interacting modes. These approaches have addressed primarily static assignment problems jointly with mode choice. Early contributions considered the multimodal version of the problem, in which an entire trip takes place by a single mode of travel from origin to destination (3–9). Trips are hence separated by mode and separately assigned to each mode’s subnetwork, with possible interactions captured through the link per- formance functions when transit vehicles and passenger cars share the same right-of-way. In these approaches, intermodal trips are modeled as a sequence of independent trips generated at the initial origin node and at intervening transfer nodes where travelers switch to differ- A dynamic trip assignment-simulation model for urban intermodal trans- portation networks is presented. The model considers different travel modes, such as private cars, buses, metro-subway, and high-occupancy vehicles. The model captures the interaction between mode choice and traffic assignment under different information provision strategies. It implements a multiobjective assignment procedure in which travelers choose their modes and routes based on a range of evaluation criteria. The model assumes a stochastically diverse set of travelers in terms of their relevant choice criteria and access and response to the supplied informa- tion. The model overcomes many of the known limitations of static tools used in current practice. These limitations relate to the types of alternative measures that may be presented and evaluated and to the policy questions that planning agencies are increasingly asked to address. Considerable research over the past decade has been directed toward modeling route choice dynamics in urban transportation networks. Most existing and proposed dynamic traffic assignment (DTA) mod- els have focused on passenger cars as the principal, if not the sole, component of urban traffic and the main source of traffic congestion. These models do not provide the capability of assigning transit trips and capturing the interaction between mode choice and traffic assign- ment. Ignoring such interaction limits the applicability of these mod- els in congested urban networks that include a considerable number of transit and intermodal trips. For instance, the DYNASMART (dynamic network assignment simulation model for advanced road telematics) simulation-assignment model (1, 2) includes buses as part of the vehicular mix; these follow prespecified routes and timetables. However, the assignment of individual trips to the transit lines and the choice of mode of travel are exogenous to the model. As such, the model’s capabilities are not sufficient to evaluate a range of intel- ligent transportation system user services targeting public transpor- tation systems (APTS) and certain advanced traveler information systems (ATIS) intended to serve transit and intermodal system users. Such capabilities require explicit representation of the supply charac- teristics of the system, in the form of a multidimensional network model of the available modes and their interaction along links as well as at nodes, and the user decision processes that govern the choice of mode or intermodal combination along with the associated path. A DTA-simulation model for intermodal urban transportation networks that provides these capabilities is presented here. The model framework is a generalization of the approach underlying the DYNASMART simulation-assignment model. The implementation is a major reengineered extension of the previous capabilities of the 52 ■ Transportation Research Record 1771 Paper No. 01- 2899