Research On Theoretical Methods Of Identifying And Reducing The Vulnerability Of High-speed Rail And Aviation Transportation Network Under Extreme Events

High-speed rail and aviation transportation networks are the backbone of domestic long-distance passenger transportation,which can meet people's needs for rapid travel.Ensuring the smooth operation of high-speed rail and aviation transportation networks has significant social and economic significance.Taking the high-speed rail and aviation transportation network as a composite network,this network expands the service scope of the domestic express passenger transportation network.In this multi-modal transportation network,passengers can complete their trip by the single transportation modes or both modes.High-speed rail and aviation transportation networks are exposed to the natural environment,and thus,extreme events like: extreme weather,mechanical failures,man-made sabotages,and others will inevitably interfere with their operations.The adverse effects caused by these extreme events will lead to a large area of train suspension and flight cancellation,seriously affecting people's travel between cities,and causing huge direct and indirect economic losses.Therefore,analyzing the vulnerability of the high-speed rail and aviation transportation network under extreme events,identifying the vulnerable nodes and areas in the network,and studying the corresponding vulnerability improvement theory have urgent practical needs and theoretical research significance.The research serves the planners of the high-speed rail and aviation transportation network,and does not focus on one of the transportation modes.The main contents of this paper are as follows:(1)A theoretical framework for reducing the vulnerability of the high-speed rail and aviation transportation network is constructed.Firstly,network science and mathematical optimization methods are combined in this paper,which are used to identify vulnerable nodes and areas in the network.Secondly,possible losses caused by the failure of vulnerable areas are took into the consideration in this framework,which influence the selection of the high-speed rail and aviation integration hub node,so as to enhance the ability of the high-speed rail and aviation transportation network to meet the travel needs of passengers.Furthermore,this framework applies mathematical optimization methods to defense the identified vulnerable nodes and reduce the overall vulnerability of the highspeed rail and aviation transportation network.(2)Based on the network science method,the vulnerable nodes and areas in the highspeed rail and aviation transportation network are identified.By extracting the connection relationship of the city at the level of infrastructure network and service line network,the transfer network corresponding to the high-speed rail and aviation transportation network that with cities as the nodes is constructed.In the study,the transfer connection strength was used as an indicator to identify vulnerable nodes and areas in the network.The study found that most of the vulnerable nodes in the network are located in East China.The areas near important main railway lines such as Beijing-Guangzhou and Beijing-Shanghai High-speed Railway Line are even more vulnerable.In addition,by comparing the overall performance changes of the high-speed rail and aviation transportation network caused by the failure of different transportation modes,this paper found that the high-speed rail network is the more vulnerable part of the high-speed rail and aviation transportation network.(3)The selection of high-speed rail and aviation integration hub nodes from the perspective of vulnerability is studied by applying mathematical optimization methods.The integration hub nodes are selected by minimizing the total passenger generalized cost.The vulnerability factors caused by extreme events with regional influence are taken into consideration.On this basis,a research on the selection of high-speed rail and aviation integration hub nodes is carried out.In the study,an integrated hub node selection model that considers vulnerability and an extended model based on this consideration of the necessity of construction are constructed.The extended model introduces parameters describing the differences in the necessity of building integrated hubs in different cities to further balance other factors that affect the selection of integrated hub nodes under normal circumstances and the vulnerability factors caused by extreme events.This model can obtain an integrated hub node selection plan that meets the actual planning scenario.Using this model,it is also possible to analyze the worst possible losses caused by extreme events.(4)This study applies mathematical optimization methods to give a method to improve the overall vulnerability of the high-speed rail and aviation transportation network by defensing the nodes in the network.This paper studies the method of avoiding possible losses caused by extreme events,by strengthening the defensing of nodes in the network before extreme events occur.This prior response method aims to improve the lower limit of the transportation network performance and reduce the vulnerability of the high-speed rail and aviation transportation network.In the research,this paper constructs a node protection model with the goal of minimizing the worst loss.On the basis of this model,by introducing uncertain sets describing the possibility of different scenarios,an extended model that considers the possibility of different scenarios is constructed.This model can use existing statistical data to make corresponding decisions.(5)Case study.In the case study,the network science methods are applied to identify the vulnerable nodes and areas,and by inputting those as known parameters into the corresponding model,the possible impact of these vulnerable areas is analyzed,then the identified vulnerable nodes can be defensed.Through the case study,the effectiveness of the proposed theoretical method is verified.