Research On Accessibility Of Multi-level Rail Transit Network In Metropolitan Area

With the accelerating process of new urbanization in China,rail transit has also shown a trend of rapid development.In the urban agglomeration and metropolitan area,a multi-level and multi-agent rail network has been formed,including trunk railway,intercity railway,suburban railway,and urban rail transit.Accessibility can measure the spatial structure,functional layout and the degree of connectivity between transport networks within cities.It converts these connections into quantitative indicators,which can better evaluate the morphological characteristics of the network and provide effective reference for planning.At present,there are few studies on the accessibility of regional multi-level rail transportation networks.Therefore,with the background of "multi network" integration,this paper studies the accessibility of the multi-level rail transit network in the metropolitan area.Firstly,this paper summarizes the multi-level rail transit development model of metropolitan area at home and abroad,and analyzes the transportation characteristics of multilevel rail transit from the aspects of circle characteristics,service characteristics and network characteristics.Secondly,from the perspective of transportation accessibility,the definition and influencing factors of multi-level rail transit accessibility are analyzed.According to the whole process of passengers choosing rail transit service for travel,the accessibility of rail transit is divided into inter-station accessibility and station-domain accessibility.This paper establishes a cumulative opportunity model based on the Point of Interest to express the accessibility of the station area,and searches the number of opportunities within the specific service area of the rail station through the route planning function of Gaode Map Application Program Interface.This paper is based on the differences in multi-level rail systems and the characteristics of connecting transfers,taking into account factors such as inconsistent running plans of opposite trains,and using the comprehensive travel cost between multi-level rail networks as the weight of network connectivity,constructing a directed weighted Space-P network that integrates multiple factors.Among them,the rail networks at different levels are compounded into an interworking network by building virtual transfer paths,and the adjacent pairs between network stations at different levels are obtained through the Gaode API path planning and web crawler,which greatly improves the accessibility of data and the accuracy of results.Then the weighted adjacency matrix is used to search the global shortest path to obtain the average travel cost of each station,so as to evaluate the inter station accessibility of multilevel rail transit in metropolitan area.Finally,taking the multi-level rail transit network of Xi’an metropolitan area as an example,the effectiveness of the model and algorithm is verified from the accessibility of stations in different levels of rail transit and the accessibility between stations in the composite network.The results show that the rail stations in the main urban area of Xi’an have the highest accessibility of the station area,and the accessibility of the railway station area is layered,gradually decreasing from the core area of the metropolitan area to the periphery;Most of the stations with the highest inter station accessibility ranking are urban rail transit interchange station located in the center of the rail network.The average travel time to other stations in the network is about 40 minutes.The five stations with the worst inter station accessibility are Zhuang Li Station,Fu Ping Station,Yan Liang Station,San Yuan Station and Yao Zhou Station located in the north of the metropolitan area,which take nearly 3 hours.