The Research On The Vulnerability Of Urban Metro Network When Sudden Interruption

Subway has become a key component in urban transport system, many cities in China have also begun to build subway network. However, the city subway system is a relatively closed system, due to the high cost of construction, the difficulty of transformation, and the completion of network construction is difficult to do large-scale changes. With the use of equipment, aging, equipment failure, natural disasters, human error, social unrest and other factors crossing, gathering and diffusion in the network, coupled with the increase of China's large urban population and subway passenger traffic,those disturbances have disturbed the safety and stability of the subway system and have resulted in frequent accidents and significant social impacts. Therefore, it is very important to study the vulnerability of the subway network under sudden interruptions and to find out the weak links and protect them, which can ensure the stability of the subway operation and the safety of the travelers and will promote the entire subway network security, stability and rapid development.First of all, this paper had summarized the relevant literature and the sudden interruption of the situation had been introduced to analyze its impact on the subway; the definition of vulnerability had been given based on the definitions in related literature and we had also introduced the research methods of vulnerability.Secondly, this paper had introduced the complex network theory and its characteristic parameters and constructed the subway network model using Space L method. We put forward six kinds of interrupt strategies:? a single node interrupt,? maximum degree of nodes interrupt, ? maximum betweenness of nodes interrupt, ? random interrupt of nodes,? a single edge were interrupted,? random interrupt of edge. The structural vulnerability of the network was analyzed by comparing the average connectivity efficiency of the network and the relative size of the maximum connected subgraph. The key sites and intervals were identified by comparing the structural vulnerability of each site and interval.And we had taken the case study of Beijing subway network in 2013 as an example.Thirdly, this paper had analyzed the social function vulnerability of the subway, and described the decrease of the network service capability after the station or interval interruption by the increase of the total cost of the generalized travel. The social function vulnerability assessment model had been established. Then, based on considering the crowded rail transit passenger flow distribution model, the time cost transportation network,the passenger route selection model, the general travel cost model and the SUE passenger flow distribution model were established. And we had chosen the appropriate algorithm to solve the general cost of the general travel of the passengers. Finally, an example had been used to verify the feasibility of the model.Finally, according to the vulnerability of the subway network, the optimization strategies of vulnerability had been discussed from the aspects of topology and social function, and we put forward the corresponding improvement measures. In the aspect of topology, this paper had analyzed the basic characteristics and vulnerabilities of three typical networks and the influence of parameters on the robustness of the network. An optimal construction method of the subway network had been put forward. For the expansion of the existing network,a method had been proposed to reduce the vulnerability of the network, and the validity of the method had been verified by an example. In view of the social function, the suggestions of improving the social function vulnerability had been put forward based on the analysis of influencing factors,which can help to prevent the accidents and optimize the emergency evacuation plan.