Modular vehicle-based transit system for passenger and freight co-modal transportation

Abstract

<p>As a solution to spatiotemporally heterogeneous passenger flows, modular vehicles allow en-route capacity adjustment to adapt to the fluctuating transport demand. This study explores the potential of integrating modular vehicles into a co-modal transport system of passengers and freight, or a modular co-modal transit system. To this end, we consider a two-way transit corridor where modular vehicles are scheduled to accommodate time-dependent passenger and freight demands. Each modular vehicle consists of several identical modules that can be individually assigned either to passengers or to the freight. A modular vehicle can alter its length (number of modules) by (un)docking modules and change the module allocation to passengers and freight (vehicle formation) at intermediate stations. With the objective of minimizing passenger waiting costs and vehicle operating costs, a mixed integer programming formulation is established that optimizes dispatch times, vehicle formation, and freight allocation. Given the solution complexity, a two-stage algorithm is proposed, where the first stage optimizes vehicle dispatch time and the second stage optimizes vehicle formation and freight allocation. Numerical experiments verify that the proposed two-stage algorithm outperforms the state of art solver and could obtain near-optimal solutions in an acceptable time for large-scale problems. A case study based on a transit line in Hong Kong validates the effectiveness of modular co-modal transit systems, where the introduction of station-wise (un)docking and co-modality could yield cost reduction by 9\% and by 13.1\%, respectively. Sensitivity analysis investigates the effect of key parameters on the performance of modular co-modal transit systems.</p>