On The Model And Congestion Performance Of Nanjing Urban Public Traffic Systems

The continued improvement of urban traffic systems,such as road network and rail transit network,has greatly facilitated people's travel.Especially in the energetically developing environment of shared bicycles,the combination of metro and bus has become a mainstream mode of urban public travel.If the operational efficiency of urban public traffic system is increased,it will be a guarantee that the transportation system operates efficiently and steadily.Since this real-time demand has attracted the attention of scholars in different fields,the analysis of urban multi-modal public transportation system network,which consists of bus system and metro system,has become a research hotspot.Aiming at this problem of public transport travel efficiency and following complex network theory,the paper analyzes the establishment of urban public traffic network model,designs a greatest influential stations discovery algorithm considering station geographical location,further evaluates urban traffic congestion performance through station cascading failures simulation.The work of this dissertation can be summarized as below:(1)On time costs for people traveling,this article presents a model of Bus-Metro weighted coupled network with time costs as network edge properties,and ulteriorly analyses travel efficiency under multi-modal transportation.And through empirical analysis that coupled spatial network is more relevant to actual travel,also reveals the cooperation and independent relationship between bus system and metro system.Travel efficiency further embodies that coupled traffic network has good performance in navigability.(2)Based on Bus-Metro coupled network topology,the consideration of station geographical location requirements,a new algorithm is proposed for finding influential stations in transportation network,which is an modified optimal path betweenness centrality algorithm.It is known from the ranking results that the optimal path algorithm considering station geographical location is more accurate than the global optimal path algorithm when ranking influential stations in transportation network by using betweenness centrality index,and the former is of high practical value.(3)Analyses were conducted on the congestion of Bus-Metro coupled network under influential stations failure,which can demonstrate the impact of influential stations with various centrality indexes on the stability and service performance of transportation system.And also the congestion performance between Bus-Metro coupled network and bus network is comparatively analyzed.The research shows Bus-Metro coupled network has character of vulnerability when a few influential stations failed,but it is more stronger than bus network for only one single mode.Meanwhile,it can be concluded that a method for evaluation of the importance of stations in traffic network presented in this paper is accurate.