Service Reliability–Based Transit Network Design with Stochastic Demand

In the study on which this paper is based, a service reliability–based formulation was developed for the transit network design problem with stochastic demand. The approach considered two types of services: rapid transit services, such as bus or rail, and flexible services, such as taxi or dial-a-ride services. The notion of service reliability was used to address the issue of stochastic demand and formulate the problem as a two-phase stochastic program in which the network and frequencies of the transit lines are determined in Phase 1, and flexible services are determined in Phase 2 depending on the demand realization. The objective was to decide the optimal combination of these two service types to minimize the total expected operating cost while serving all realized origin–destination demands. The transit line alignment and passenger flow distribution pattern were studied under system optimal flows. A gradient solution approach was developed to solve the problem. An illustrative example was constructed to demonstrate the performance of the solution algorithm and the advantages of the combined services as compared with rapid transit or flexible service alone under stochastic demand.