Vulnerability Assessment and Optimization of Urban Rail Systems Against Extreme Perturbations: A Case Study on the Zhengzhou Metro Flooding

Abstract

With the rapid development of urban rail networks in recent years, these complex transportation systems are facing significant challenges in both preparing for and recovering from the growing impact of extreme perturbations caused by various factors such as extreme weather, equipment faults, and security threats. Assessing and improving the vulnerability of urban rail systems to perturbations is crucial for ensuring efficient and safe mobility services for passengers. While most existing studies have focused on the vulnerability assessment of physical transportation networks from the perspective of infrastructures, our study aims to investigate the vulnerability of urban rail systems to extreme perturbations from the perspective of rail managers. Specifically, for the assessment of system vulnerability, we first construct a graph model with the definition of nodes, edges, and edge weights using a hybrid DEMATEL-ISM-ANP method to capture the causal relationships among different factors leading to perturbations, such as technical system factors, organizational factors, and human factors. Then, for the optimization of system vulnerability, we develop a mixed integer programming (MIP) formulation based on the constructed graph model to identify the most vulnerable factors against perturbations. We implement our approach in a case study of the Zhengzhou metro flooding disaster, which occurred on Zhengzhou metro line 5 on July 20, 2021, resulting in the death of 14 passengers. The results indicate that our approach can correctly identify the factors that significantly influence system vulnerability in the Zhengzhou metro flooding. Our findings support that the Zhengzhou metro flooding disaster was primarily caused by human factors, such as the failure of emergency commands from dispatchers. We also conduct experiments to draw valuable insights for early warnings of urban rail systems against extreme perturbations.

Keywords: Urban rail transit, Vulnerability assessment, Network flow, DEMATEL-ISM-ANP, MIP