Formulation of Analytical Time-Varying Intermodal Person Trip Assignment Model

An analytical formulation of the intermodal dynamic traffic assignment problem is presented. The model is a cell transmission-based, single-destination, system optimal integer linear programming formulation for a multimodal network of cars and buses. The computational tests demonstrate interesting insights into the complex interactions between travelers' intermodal path choices and traffic movements. Specifically, as with many analytical time-varying traffic models, the constraints regulate flow, while the objective function provides an incentive for travelers to progress on least-cost paths toward the cost-free trip termination cells. It is found that difficulties relate to this reliance on costs to advance travelers and vehicles; for example, the non-first-in-first-out propagation of buses ahead of automobiles is a result of the higher cost incurred by numerous riders on a single bus vehicle. Similarly, the model's tendency to hold buses at bus stops or force buses to skip bus stops results from a difference in costs incurred by travelers who would be better served by the holding of the bus or by the skipping of a stop. On the basis of the findings on the model's behavior, recommendations are made for the future development of time-varying intermodal routing problems.