Robustness assessment of urban rail transit based on complex network theory: A case study of the Beijing Subway

A rail transit network usually represents the core of a city's public transportation system. The overall topological structures and functional features of a public transportation network, therefore, must be fully understood to assist the safety management of rail transit and planning for sustainable development. Based on the complex network theory, this study took the Beijing Subway system (BSS) as an example to assess the robustness of a subway network in face of random failures (RFs) as well as malicious attacks (MAs). Specifically, (1) the topological properties of the rail transit system were quantitatively analyzed by means of a mathematical statistical model; (2) a new weighted composite index was developed and proved to be valid for evaluation of node importance, which could be utilized to position hub stations in a subway network; (3) a simulation analysis was conducted to examine the variations in the network performance as well as the dynamic characteristics of system response in face of different disruptions. The results reveal that the BSS exhibits typical characteristics of a scale-free network, with relatively high survivability and robustness when faced with RFs, whereas error tolerance is relatively low when the hubs undergo MAs. In addition, illustrations of dynamic variations in the influence of the BSS under a series of MAs were provided by spatial analysis techniques of Geographical Information System (GIS), which directly verified the earlier conclusions. We believed the proposed methodology and the results obtained could contribute to a baseline for relevant research of transportation topological robustness.