Bi-Level Optimization Model for Public Transportation Network Redesign Problem

Spatial equity is an extremely important issue in both design of a new and redesign of an existing transit (and highway) network because it is concerned with the benefit distribution among transit (and highway) network users. This paper presents a hi-level optimization model-in which the spatial equity issue is explicitly considered for the first time-for solving the public transportation network redesign problem (PTNRP). The goal of the upper-level subprogram is to minimize total cost, including user cost, operator cost, and unsatisfied demand cost, for the studied bus transit network, subject to a variety of resource- and policy-related constraints. The lower-level subprogram is a user self-routing optimization problem in which all transit users try to find the transit route to minimize their own travel cost (or time) and number of transfers in the network. Then, a procedure for a genetic algorithm-based solution is developed to solve this PTNRP hi-level optimization model. Network experiments are conducted, and numerical results are described. Future research directions are also given.