Research On Cooperative Optimization And Cascading Failure Evolution Of Metro-Bus Network Based On Double-Layer Coupling Network

Urban rail transit is the backbone transportation mode of urban public transportation.It has the advantages of large capacity,power and environmental protection,on-time operation,high efficiency and fast.It has gradually become the leading force to solve the chain congestion and traffic pollution problems in large cities.In China,the scale of urban rail transit lines has developed rapidly,and urban rail transit in major cities is gradually forming a networked operation pattern.With the network operation of rail transit,the development of rail transit road network structure,transfer organization and driving organization means has become more complicated and diversified.At the same time,the subway and bus network are the main modes of transportation in the urban transportation network.The cooperation between the subway and the public transport double-layer network plays an important role in exerting the effectiveness of the public transport system.Therefore,optimizing the dual-layer network structure is the key to establishing an efficient collaborative system.At the same time,the urban transportation network is also a huge and complex system,and its operational safety is crucial.Especially with the continuous expansion of the scale of the subway line network,daily emergencies continue to increase.In this case,once an emergency occurs,it will not only cause the station to fail and stop,it may seriously cause cascading failures of the entire subway line network.Therefore,there is an urgent practical need to study the passenger flow dynamics after the subway is under attack.The main work and results of this article are as follows:(1)This paper introduces the double-layer complex network theory,and uses the multi-layer representation method of the urban transport network to description and explain the mutual cooperation and influence of the two levels of the subway and the bus network,and build a subway-bus double-layer coupling network model through the double-layer complex network theory,based on this,the route selection and traffic flow dynamics of the transportation network,and further study the collaborative optimization and cascading failure evolution on the metro-bus coupled double-layer transportation network.Its purpose is to use the current network characteristics and changes in passenger behavior to determine the best structure under the current network scale,as well as preventing large-scale cascading failures in urban public transportation networks,planning overall defense strategies for cascading failures of transportation network nodes,In order to improve the network efficiency of the subway-bus transportation network and the invulnerability of the network.(2)A mutually collaborative two-layer urban traffic network collaborative optimization method was presented.In order to solve the problem of the coordination in the transfer process between the Metro-Bus network in the urban transportation network when the passengers make the route selection,such as the distance between some transfer stations is too far,the connection orientation is not clear,and the partial transfer supply and demand imbalance,a collaborative optimization method for urban traffic networks based on two-layer complex networks was presented.Firstly,the logical network topology method is applied to the topology of the urban transportation network,and the Metro-Bus double-layer network model is established by the complex network theory.Secondly,taking the transfer station as the research object,a method of node importance evaluation by K-shell decomposition method and central weight distribution was presented.This method can divide and identify coarse and fine-grained subways and bus stations in large-scale networks,and a mutually collaborative two-layer urban traffic network collaborative optimization method was presented.Complex network theory is introduced into two-layer network structure optimization to identify and screen the importance of nodes in network topology.The double-layer network structure is updated by identify high-aggregation effects and locate favorable nodes in the path selection to optimize the layout and connection of stations of the existing network.Finally,the method is applied to the Chengdu metro-bus network,the existing network structure was optimized,get the optimal optimized node location and number of existing networks,and the effectiveness of the research results is verified by the relevant index system(3)The evolution of the cascading failure of the subway network is studied,considering the differences in the passenger flow direction attributes of the nodes of the subway network,and the actual path selection behavior of passengers in different node directions when encountering the failure of the subway node,We propose a cascading failure model considering the direction of node passenger flow,and introduce the double-layer coupling network mechanism of the bus network to avoid the subway network from being triggered by a large-scale cascading failure failure after being attacked,Taking the intensity of passenger flow in a complex network node based on passenger flow as the initial load,and the traffic flow in the direction of the failed node is reloaded using the delayed traffic loading method during the duration of the failure;Reloading of passenger flow in the failure direction Considering the subjective factors of passengers' path selection after node failure and the optimal loading direction for passenger flows in different directions,the dynamic selection effect of passenger reloading in the failure direction is determined based on the prospect theory.The model uses the improved Frank-Wolfe to load the original OD traffic of the network to solve the road segment,path and node direction passenger traffic.Finally,the FW-MSA algorithm is used to solve the model;And use Chengdu metro network to verify the example,and simulate the dynamic loading of passengers at the failed node.Simultaneously,by simulating different attack intensities and different threshold levels,the cascading failure evolution of the Chengdu metro network under the conditions of access to the bus network and non-access to the bus network,there is a clearer explanation for studying the micro dynamics of subway stations after being attacked.