SORTAH: System Optimal Re-Routing Transit Assignment Heuristic

Traditionally, transit networks are modelled to follow the user equilibrium principle where passengers take a path that would benefit them the most. This does not directly address the system perspective and results in inferior performance compared to the pure system optimal model for congested networks. This research presents a new framework for the transit assignment problem to address the system perspective of an overcrowded transit network while integrating individual travel needs. It proposes a novel approach called System Optimal Re-Routing Transit Assignment Heuristic (SORTAH) that minimizes the overall congestion effects on a transit network. SORTAH leads to a better performing solution than that of a user equilibrium model, while simultaneously guaranteeing superior fairness compared to the pure system optimal model. A proof-of-concept prototype is implemented to compare network performance of the user equilibrium solution and the SORTAH solution. A large-scale real-world application is conducted on the Toronto Transit Commission (TTC) network.