Vulnerability Comparisons of Various Complex Urban Metro Networks Under Multiple Failure Scenarios

Urban metro networks, characterized by their complex systems of interdependent components, are susceptible to a wide range of operational disturbances and threats. Such disruptions can cascade through the system, leading to service delays, operational inefficiencies, and substantial economic losses. Consequently, assessing and understanding network vulnerabilities have become crucial to ensuring resilient metro operations. While many studies focus on single-failure scenarios, comparative vulnerability analyses of various urban metro networks under multiple or simultaneous failures remain limited. To address this gap, our study introduces a comprehensive analytical framework comprising three key components: quantitative indices operating at both network and node levels, methodological approaches to assess the importance of network components (nodes, edges, and lines), and systematic protocols for evaluating vulnerabilities across multiple failure scenarios (stations, tunnels, lines, and areas). A comparative analysis of the Shenzhen Metro Network (SZMN) and the Zhengzhou Metro Network (ZZMN) validates the proposed methods. The results indicate that the SZMN demonstrates higher connectivity and accessibility than the ZZMN, despite a lower network density. Both networks are disassortative and heterogeneous, with edges connecting multiline transfer stations showing significantly higher edge betweenness centrality compared to those connecting general stations. In the SZMN, 6.63% of node failures and 4.74% of tunnel failures exceed a vulnerability threshold of 0.03, compared to 13.74% and 11.27% in the ZZMN. Failures across different lines and areas yield varying impacts on network performance and vulnerability. This study provides essential theoretical and practical insights, helping metro safety managers identify vulnerable points and strengthen the sustainable development of urban metro systems.