Analysis On Structural And Functional Survivability Of Urban Rail Transit Network Based On Failure Of Important Stations

Urban rail transit has rapidly developed into the main public transport mode in the city with its characteristics of arrival on time,large capacity,low carbon emissions and environmental protection.When the urban rail transit network is affected by accidents,natural disasters and terrorist attacks and the failure of stations,the network structure of urban rail transit will be damaged and the transport capacity of the network will be reduced,thus resulting in lower travel efficiency of the network and lower travel service level of passengers.The ability of the urban rail transit network to maintain transport efficiency,meet the original passenger demand and maintain a certain level of passenger service is the structural and functional survivability of the urban rail transit network,after these transport accidents happened.The characteristics of Wuhan metro network are analyzed by using complex network theory and passengers' travel data during morning peak hours.It is found that the characteristics of Wuhan metro network can be reflected more comprehensively and truly by combining passenger flow analysis.In order to evaluate the structural survivability of urban rail transit network comprehensively,the global survivability indicator,the OD connectivity survivability indicator and the travel success rate of the urban rail transit network are proposed.The mean value of the three indicators is taken as the comprehensive indicator of the survivability of urban rail transit network.Importance of connectivity of stations are identified by dynamic identification method of importance station.Important stations in the network are determined by stations' degree,stations'betweenness and stations' betweenness considering passenger flow.Taking Wuhan metro as an example,the structural survivability of Wuhan metro network is analyzed under the complete failure of important stations' capacity.The simulation result shows that the survivability of Wuhan metro is weak in the face of attacking important stations deliberately.The attack on importance of connectivity of stations leads to the fastest decline in the structural survivability of Wuhan metro network.It means that the importance of connectivity of stations identified by dynamic identification method of importance station is effective and accurate.Importance of connectivity of stations that take into account passenger flow have the largest impact on structural survivability of Wuhan metro network.It means that the structural survivability of Wuhan metro network can be reflected truly with passenger flow considered.The functional survivability of the urban rail transit network is evaluated by the increased rate of passengers' generalized travel expenses before and after the partial capacity failure of important stations.The passengers' generalized travel expenses are calculated by stochastic user equilibrium distribution model.The functional survivability of Wuhan metro network is analyzed by simulating the decline of some important stations'capacities.The simulation result shows that the station with the greatest impact on the functional survivability of Wuhan metro network has the following characteristics:The station is located in the middle of the line,the station is in the central area of the city,passenger flow of the station's the adjacent section is large,and the station' adjacent station is transfer station."The simulation result also shows that important stations are determined by stations'betweenness considering passenger flow have a great influence on functional survivability of Wuhan metro.