Abstract
Metro network is the important lifeline in modern cities. Its stability and reliability are critical for guaranteeing the urban residents' efficient commuting and continuous operation of urban functions. A series of disruptions show the vulnerability of metro network, and even the breakdown of a single node is sufficient to collapse the entire network due to cascading failure. However, the vulnerability assessments of metro network in the previous studies neglect the impact of cascading failure on the drop of network service performance. This paper measures the vulnerability of metro network by capturing the demand loss and travel delay under cascading failure. First, a load-capacity based model is developed to describe the dynamic process of cascading failures. Then, a weighted composite index composed of demand loss and travel time delay under cascading failure is used to measure metro network vulnerability. Finally, taking Shanghai metro network as an example, five attack scenarios are simulated to investigate cascading failure process and network vulnerability. The results reveal that cascading failures result in severe consequences in the metro network. The vulnerability of metro network without considering cascading failure is underestimated. The decrease in the tolerance parameter leads to the increase in metro network vulnerability. Random attack on one node is the most sensitive to the tolerance parameter. Node betweenness, cascading failure path and the initial load on the overloaded nodes also affect metro network vulnerability. This study provides a new perspective for understanding vulnerability of metro network, and also provides insights for improving operation reliability and stability of the network, as well as for designing emergency strategies to protect the network.
Highlights
With the advantages of large capacity, punctuality and fast speed, metro network is the lifeline of metropolitan cities, playing a prominent role in alleviating traffic congestion in metropolis areas
On August 10, 2020, Metro Line 16 encountered a power failure caused by lightning strikes, which led to service delay and overcrowding in Shanghai due to passengers rerouting their paths in the disrupted network
This paper aims to fill this gap by measuring vulnerability of metro network from the system-based perspective by taking into account cascading failure
Summary
With the advantages of large capacity, punctuality and fast speed, metro network is the lifeline of metropolitan cities, playing a prominent role in alleviating traffic congestion in metropolis areas. This paper will capture the unsatisfied demand and the travel delay under cascading failure to measure vulnerability of metro network. In the field of public transport network, Zhang et al [27] constructed a cascading failure model of weight public transit network, where the link prediction effect is considered in FLDR. He et al [31] proposed a transfer-based path navigation strategy to describe the flow distribution rule of transit network. Liu et al [32] improved the cascading failure model of metro network in previous studies by proposing an improved edge weight function to analyze the change of node state. It is necessary to analyze the failure process of metro network, and propose a cascading failure model that is more in line with the metro system
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