Analysis And Optimization On Connectivity Reliability Of Urban Rail Transit Network Based On Topology

With the continuous development of urban rail transit system, the reliability of the network is gained more and more attention, In recent years, the rail transit network of many big cities including Nanjing always adds new lines into the original lines. With the expansion of the rail network scale and the improvement of network function, the proportion of urban rail transit in urban public transport is increasing, which means people put forward higher requirements to process daily things and the reliability and resilience of urban rail transit network under disaster situations.Topological structure of urban rail transit network has a significant impact on the connectivity reliability of network. The network will produce what kind of impact when the rail network nodes or edges are attacked is worthy of attention. Thus, the studies of the reliability of urban rail transit network based on topological structure have important theoretical and practical guidance significance on reasonable expansion of urban rail transit network, identifying weak links in the network and developing a reasonable contingency plans to deal with emergencies.Therefore, starting from the network topology, this article firstly selects the cities in economically developed countries or regions at home and abroad which construction is into a net, and analyzes the basic characteristic of the urban rail transit network including average degree, average betweenness, average path length, average aggregation coefficient. After that we get the number of sites and the number of edges have positive linear relationship, while the number of sites and the average betweenness, the number of edges and the average betweenness have exponential relationship. In addition, degree distribution can be approximately considered as gaussian distribution. Then, the article takes 2030 Nanjing planning metro network as example, establishs connectivity reliability evaluation indicators. Through analyzing the sensitivity of these indicators by adopting four different network attack strategy patterns which are the initial degree(ID), the initial betweenness (IB), the round degree (RD) and the round betweenness(RB), the article gets the average path length is the best analysis indicator which can reflect the Nanjing metro network connectivity reliability. Finally, the article establishs connectivity reliability optimization model under constraints of cost, and obtains creating seven lines is the best optimization to improve the connectivity reliability of Nanjing metro network by comparing.