The Robustness Of Urban Public Transportation System:the Double-layered Network Perspective

The sustainable development of a city requires the support of a safe and reliable urban public transportation system.In-depth analysis of the urban public transportation network’s topological structure characteristics and its passenger transfer performance is helpful for better transportation planning and management.First of all,this study constructed a double-layered complex network of urban bus and subway based on the complex network theory.Then,the average shortest path length(APL),the relative size of giant component(RSGC),and the global network efficiency(GNE)are selected as structural indicators to quantify the structural robustness of the bus-subway double-layered complex network;the passenger flow loss rate(R)is selected as indicator to measure the functional robustness of bus-subway double-layered complex network.Thereafter,a cascading failure model of bus-subway double-layered complex network based on the nonlinear load-capacity model is proposed,and the dynamic passenger transfer rules during the cascading failure process are set.Finally,taking the bus and subway system in seven major urban areas of Xi’an as an example,a bus-subway double-layered complex network in Xi’an urban area is constructed.The robustness of the network under different attack strategies is analyzed through MATLAB simulation program.The research results are showing as follows.(1)The capacity control parameters αand β have a significant impact on the cascading failure process of bus-subway double-layered complex network in Xi’an urban area.The 0.01 increment of parameter βor a 0.04 decrease of parameter α can significantly enhance the ability of network to resist the cascading failure.(2)By attacking the node with highest node degree,the Xi’an urban bus-subway double-layered complex network achieves high robustness under the optimum node capacity of α(28)0.15 and β(28)0.27.(3)In general,the robustness of Xi’an urban bus-subway double-layered complex network under the random attack mode is stronger than the deliberate attack mode.(4)The bus-subway double-layered complex network in Xi’an urban area is vulnerable to the mixed attack mode.(5)The strategy of increasing network node capacity has better effect on improving the robustness of the bus-subway double-layered complex network in Xi’an urban area than the key node protection strategy.By rationally planning the capacity of the network nodes,the robustness of the bus-subway double-layered complex network in Xi’an urban area can be significantly improved.This study analyzed the robustness of the bus-subway double-layered complex network under three attack modes from the two dimensions of network structure and passenger transfer performance.This study further enriches the research on the robustness of public transportation networks.The research results provide a decision basis for improving the robustness of the public transportation network.