TRANSIT SERVICE AND PATH CHOICE MODELS IN STOCHASTIC AND TIME-DEPENDENT NETWORKS

This paper develops a new path choice model that incorporates both tim e-dependent and stochastic transit service characteristics, and allows passengers to update path choice decisions while waiting. To develop this model, a new transit service model is proposed that represents ro ute segments using a shuttle model. Such a model balances requirements for stochastic and time-dependent service modeling with the ability t o aggregate to a larger transit corridor or network. This service mode l leads to a dynamic model of transit path choice, in which the passen ger may wait until a vehicle is about to depart before making a boardi ng decision. A formal definition. of this dynamic path choice model is given, and its differences with previous path choice models are noted . Based on, this definition, two mathematical formulations of the dyna mic model are developed. The first formulation assumes that the passen ger will use the dynamic model for all possible vehicle departure time s in the future, and is formulated as an optimal control problem. It i s shown mathematically that this problem formulation is a less-constra ined version of previous path choice models. However, because of some analytic and behavioral difficulties with this first model, a more wel l-behaved constrained formulation is also presented. A smalt corridor example demonstrates the significant differences in path choices and t ravel times between the constrained dynamic model and more traditional path choice models. Limitations of these dynamic path choice models a re also discussed.