Enhancing urban rail transit resilience: Strategic bus resource allocation

Urban rail transit (URT) systems are integral to urban mobility but are susceptible to disruptions that can substantially impact service continuity and passenger convenience. The increasing incidents of URT disruptions necessitate effective strategies to ensure robust and resilient transit operations. Temporarily requisition regular buses to serve as bridging services has become a common strategy to mitigate the adverse effects of URT service disruptions. This study investigates a novel macro-level integration planning problem of regular buses, aiming to optimize both regular bus resource allocation (including depot location, vehicle fleet and vehicle-to-line assignment) and bus bridging services in response to URT disruptions (including the mapping relationships between regular bus depots, requisitioning buses and URT stations), with the goal of minimize operational disruptions and enhance service reliability. A bi-objective integer programming model is developed to integrate regular bus service planning with bus bridging services in response to URT disruptions, minimizing the total deadheading time and reducing the number of unserved passengers. An augmented ε-constraint method, combined with lexicographic optimization and a utopian point, is proposed to generate balanced Pareto optimal solutions. The model is tested through case studies involving both small-scale (part of the Nanchang Metro network) and large-scale (entire Nanchang Metro network, Nanjing Metro network and Chengdu Metro network) disruptions, based on real-world data. Results demonstrate that our approach can produce high-quality solutions that significantly enhance the operational efficiency and responsiveness of bus services to URT disruptions. These strategies ensure smooth operation of regular bus services, mitigate the impacts of URT disruptions, and promote cost-effective utilization of bus resources.