Robustness of Urban Rail Transit Networks Considering Cascade Failure under Attacks: A Case Study of Nanjing, China

Urban rail transit (URT) has become one of the main carriers to undertake passenger transportation tasks in large and medium-sized cities. However, station failures can reduce the efficiency of passenger travel and the transport capacity of the entire network. This paper constructs an urban rail transit network (URTN) topology model based on complex network theory and builds a cascade failure model considering load redistribution, five attack strategies, and three load distribution strategies. Then, the transport capacity is taken as a comprehensive metric of network robustness and the effects of different attack strategies, different load distribution strategies, and different parameter values on the robustness of URTN are compared. Finally, the Nanjing rail transit network is used as the case study. The Intentional Attack (IA) strategy is more destructive to the transport capacity than the Random Attack strategy. The network robustness under the Static Intentional Attack (SIA) strategy is weaker than that of the Dynamic Intentional Attack (DIA) strategy. Given different load distribution strategies, the levels of network damage based on the station degree and the betweenness of the attack strategy are different. The residual capacity load distribution strategy can significantly improve the robustness of the network. The robustness of the network can be improved by adjusting the coefficient of the capacity regulation and passenger transfer rate and can be optimized when the coefficient of capacity regulation is in the interval of [0.6, 0.8] and the passenger transfer rate is in the interval of [0.3, 0.4]. The proposed methods can be applied to assess the robustness of an URTN and offer operators an alternative to formulate safety operational management strategies.