Topology Vulnerability Analysis and Measure of Urban Metro Network: The case of Nanjing
Urban metro network system is the most effective solution for relieving traffic congestion in large cities. With the development of metro, vulnerability analysis is a core process of metro safety management under the condition of network operation. In this paper, Nanjing planned metro network, in china, which was investigated and analyzed based on the graph theory complex network theory. The metro network topology characteristics and functional properties can be studied by Space L model. Several parameters were used to analyze and measure the topology vulnerability. The fraction of removed nodes is discussed and quantitatively compared in different protocols; meanwhile, the critical threshold of the fraction is 0.05-0.07. The study indicates that Nanjing planned metro network sharing some similar characteristics with those of scale-free network and small world network simultaneously; the metro network is robust against random attacks but vulnerable to malicious attacks; two parameters called global efficiency and average path length were proposed to measure the vulnerability of metro network. In the quantization of vulnerability, both betweens and degree need to be comprehensively considered, because parameter value and its influence are not absolutely positively correlated; In the end, a qualitative calculation method is proposed to calculate the node or vulnerability based on global efficiency and average path length.