Resilience Assessment And Critical Station Identification Of Urban Rail Transit Network Considering Bus Bridging

As an important urban infrastructure,urban rail transit network is vital to economic development and daily travel of residents.As the scale of urban rail transit network expands,its risk of disaster and damage is also increasing.Once rail transit network fails,the impact will be huge.Therefore,it is necessary to analyze the failure impact of different network units of rail transit network and the speed of network recovery.Through analysis and research,the critical infrastructure of urban rail transit network can be identified.Thus,urban rail transit management departments can take appropriate measures to reduce the impact caused by unexpected events and ensure reliable operation of urban rail transit network.The resilience of rail transit network mainly depends on the failure impact of network units and the time to restore network to normal operation under unexpected events.In the assessment model of the magnitude of impact caused by network unit failure,most scholars ignored the characteristics of evacuation of passengers through bus bridging after an emergency,which would overestimate the impact of sudden accidents on passengers.In the urban rail transit network recovery stage,existing studies lacked quantitative evaluation of network recovery time.In addition,in the research of rail transit network critical station identification,most researches ignored the length of network recovery time after station failure.Therefore,based on the necessity of the research and the deficiencies in current research,this paper investigated the quantification method of urban rail transit network resilience and the identification method of critical station.The research contents and innovations of this paper main include four aspects.First,a quantitative assessment model of urban rail transit network failure impact considering bus bridging was constructed.The model overcame the shortcomings of previous studies that overestimated the impact of rail network failure by ignoring the evacuation characteristics of passengers via bus bridging during unexpected events.Second,an emergency rescue station location model considering the failure impact of different rail transit network stations was constructed.On the basis of satisfying the constraints on the number of rescue stations and the maximum emergency rescue distance,the model also made the emergency rescue stations as close as possible to the stations with high failure impact in order to reduce the impact caused by emergency events.Third,a method quantifying network recovery time considering the location of emergency rescue stations and the allocation of rescue resources was proposed.And then this paper proposed a quantitative model of urban rail transit network resilience based on the severity of the impact caused by network failures and the length of network recovery time.Fourth,a resilience-based critical station identification method for urban rail transit networks was presented.The method overcame the shortcomings of previous critical station identification methods that only considered the impact of station failure but ignored the length of network recovery time.The importance of rail transit network station was analyzed from two dimensions which include the impact of station failure and the time of network recovery.The research results show that the magnitude of failure impact of a station is not only related to the volume of passengers entering,leaving and passing through the station,but also related to the degree which different passengers are affected by unexpected events.The failure impact under multi station failures depends not only on the importance of each station,but also on the relevance between different stations.Second,bus bridging can significantly reduce the impact of rail network emergencies on passenger travel.Network performance loss can be reduced by 4.81% with considering bus bridging after the failure of a single rail transit station.Thirdly,compared with the average distribution of rescue resources,the optimized allocation of rescue resources by emergency rescue stations in this study can shorten network recovery time after a multi-station failure by 35.37%.Fourth,stations with higher failure impact and longer network recovery time have relatively lower values of rail network resilience once an emergency event occurs.The network resilience value is also relatively low for stations with low failure impact but long recovery time,and stations with short recovery time but high failure impact.In actual operation management,urban public transportation management and emergency management departments should strengthen management of the stations located on ring line and the radial line of the ring line.The impact of rail transit station failure can be reduced by optimizing bus routes and bicycle sharing,and the network recovery time can be shortened by increasing the rescue resource reserve and setting up more emergency rescue stations,thus improving the resilience of urban rail transit network.