Exploring metro reliability under synchronous cascading congestion induced by line perturbation

Abstract

In metros, line perturbation caused by local accidents can affect all the stations on the same line. Moreover, this impact can spread to other lines through line interaction, leading to network synchronous cascading congestion and bringing great risk to metros. This paper proposes a cascading model to study the synchronous congestion spreading mode and metro reliability under line perturbation. In the model, the station carrying capacity is calculated based on system balance and evolves through congestion spreading, line perturbation, and line interaction, realizing the full coupling of stations on metro line. The passenger behaviour is considered by an impedance function combined with station state and traffic condition. Nanjing metro is studied. The results reveal a multi-point synchronous congestion extension mode of the network under line perturbation and interaction. Moreover, larger line perturbation and interaction can lead to faster congestion spreading and a larger decline of the network reliability, but the congestion risk can gradually decrease with the increase of hops along lines. High station tolerance, turn back mode, and train frequency adjustment of transfer lines and segment lines are beneficial to the network reliability. The optimal train frequency adjustments of transfer lines and segment lines are also obtained by limiting congestion spreading. This paper provides theoretical supports for synchronous dynamics of metros and cascading reliability analysis. The methods and findings can be extended to other networked systems to address the cascading reliability with multi-point synchronization congestion.