Research On Key Nodes Identification Method Of Urban Public Transit Network Based On Complex Network

Urban public transportation,with its advantages of large capacity,low energy consumption,less pollution,strong safety,and reliability,has become a significant mode of transportation for people,effectively relieving traffic congestion.At the same time,the urban public transport network system is a relatively closed and a kind of high density of people system.As a whole system,it not only has the basic characteristics of a complex network but also has the dynamic characteristics caused by the temporal and spatial uncertainty of passenger flow.Once the key nodes(stations)in the public transport network(PTN)are damaged,it will cause great damage not only on the key nodes and relatively lines but also on the stability of the whole PTN,especially considering the highly concentrated characteristics of morning and evening peak passenger flow in big cities.Hence,the identification and protection of the key nodes of the PTN have become the most important work of the urban public transportation system operation management.At present,indicators used to identify key nodes in PTN mostly rely on network topology,and there are little researches on key node identification methods considering the impact of loading passenger flow and passenger supply and demand.Therefore,based on the physical structure of the PTN and the actual travel needs of passengers,this study proposed the measurement indicators and identification methods of key stations considering the comprehensive characteristics of the PTN for different scenarios,which can provide theoretical support for the planning,design and operation management of the PTN.Meanwhile,it can also provide a basis for strengthening the protection of key nodes to improve the response speed of PTN in emergencies and ensure the safety of passengers.Based on complex network theory,starting from the PTN elements and complexity analysis,this paper studies the PTN modeling method and analyzes the PTN topology characteristics.On this basis,it combines the characteristics of station passenger flow in PTN to put forward a key node identification method for PTN’s characteristics and the demand of daily monitoring.Then,considering the acceptable travel time thresholds of passengers,the weight increment model of public transport routes is built,and the set of alternative paths between OD pairs is established.Then,the refined identification method of key nodes of PTN based on the global path is proposed.Finally,combined with the factors affecting the PTN emergency,considering the information of station passenger flow,network topology information,the spread of the epidemic,acceptable travel path,and so on,the key node mining method of PTN under the emergency is proposed.Specifically,the research work of this paper mainly includes these four aspects:(1)Combing the public transport network elements and complexity and the complex networks theory,a modeling method that suit the character of the public transport network is discussed.Based on statistical index of static structure of complex network,the characteristics of static topology of PTN are analyzed.Then,the visualization software Gephi is used to construct the Beijing public traffic network modeling.Based on the static structure index of complex networks,the analysis of ground public transit network and the structural characteristics of rail transit network are realized and identify the key stations in the topology of PTN.The research results can provide a basis for the identification of key nodes of PTN in different scenarios.(2)Based on the topological importance of PTN and the characteristics of passenger flow at stations,a key node identification method in the urban transit network is proposed under the local influence of nodes.Using the massive public transportation IC card data,the passengers’ flow of PTN’s stations in different periods in all days is extracted.Then,combining the important parameters of network structure,the key stations’ influence model of PTN is proposed and verified the model based on simple network and network efficiency.Comparing with the present evaluation method of the key nodes,the ones identified by the model in this study are attacked,the network efficiency decreases fastest.Based on the model constructed in this study,the key stations of Beijing bus network are identified.Meanwhile,their spatial distribution is analyzed,and the formation mechanism of key stations is revealed.The results can improve the one-sided problem caused by the use of single indicators in previous studies,which also can provide theoretical support for the early planning and subsequent adjustment of PTN.(3)Based on the characteristics of network topology,route reliability and individual actual travel path,the global route diversity index is proposed to identify the key nodes in PTN.By integrating the routes and stations information of ground bus and rail transit,the joint principle of the multi-mode public transport stations’ walking transfer is defined.Then,multi-mode bus network stations as nodes and line sections and passenger transfer paths as edges are established.Moreover,considering the topological importance of stations,line reliability,and acceptable travel time constraints of passengers,a line weight increment model is built to generate the set of alternative routes between any OD pairs.Based on the set of alternative routes,the global route diversity is proposed as an index to evaluate the importance of nodes in multi-mode PTN.Then,the key stations of Beijing multi-mode PTN are identified and their spatial distribution is analyzed.The research results further shorten the distance between the theoretical method of critical station identification in multi-mode PTN and the refined monitoring requirements in actual operation management.Meanwhile,it can provide a set of highly reliable alternative paths between any OD pairs,providing a scientific method for passenger flow assignment and vulnerability evaluation of PTN.(4)Integrating the spatial distribution of the epidemic,topological characteristics of the PTN,supply and demand of the passenger flow,a method to identify key nodes of the urban PTN in emergencies is proposed.Through the analysis the emergency influence on PTN,combined with the impact of COVID-19 and the demand for regular epidemic prevention,buffer zones at railway stations are constructed to characterize the impact of the epidemic risk.Considering the passenger flow at stations,network topology and other factors,a reasonable route set between any OD in the rail transit network and the path risk model in an emergency are established.Then,an influence model of rail transit station is proposed under the reasonable route set.Identifying the key stations in Beijing’s rail transit network,the Coupled Map Lattices(CML)model is used to attack the key stations deliberately and evaluate network stability.The research results can provide a theoretical basis for public transport managers to identify risk stations in the network and provide passengers with reasonable and effective alternative routes in case of emergencies in the PTN.