Assessing metro network vulnerability with turn-back operations: A Monte Carlo method

Abstract

Metro network disruptions caused by accidents or maintenance can significantly impact its serviceability. Traditionally, graph theory and complex network methods are utilized to examine topological properties by removing nodes, links, or entire lines. However, in practice, it is the turn-back operation that determines the service cancellations and the affected area. This study assesses metro network vulnerability by considering the turn-back section as the Vulnerability Analysis Unit (VAU). Indicators for evaluating topological accessibility and operational robustness are proposed to assess network performance under disruptions. Monte Carlo method is applied to generate scenarios, involving the removal of various combinations of VAUs. A case study is conducted on Shanghai Metro system. The results indicate that on average, when one VAU is damaged, the travel time will increase by 2.39 minutes and 1.75 % of passengers will move to other transport modes. The critical vulnerable sections are mainly located in radial lines connecting to the loop lines, while those located in or inside the loop line exhibit higher robustness.