Rail Transit Network Generation Based On Network Community Structure

With the rapid development of urbanization,urban traffic problems have become increasingly prominent,and the development of urban rail transit systems has effectively alleviated the traffic pressure of urban road systems.However,in the development of China's railway transit,there are problems such as passenger flow congestion and difficulty in transfer.Part of the reason is that the original line network planning scheme is not compatible with the urban spatial structure.Considering the large scale and irreversible characteristics of rail transit construction investment,it is of great significance to accurately analyze the urban spatial structure and plan the rail transit network that meets the travel needs of residents and adapts to the development of urban space.By summarizing the current rail transit network planning methods,it is found that there is no quantitative analysis method in the existing methods,and the scheme is subjectively influenced by the planners,resulting in a large randomness of the network planning scheme.Therefore,the purpose of this paper is to quantify the process of network planning,and propose a method of urban rail transit network planning based on network community structure,aiming to reveal the urban spatial structure by urban activity model,and then generate a matching network plarning scheme.Firstly,the definition and classification of complex network community division are introduced.The four typical community division algorithms based on modularity are introduced,and the quality evaluation based on modularity(Q),standardized mutual information(NMI)and algorithm complexity is introduced.The indicators are compared with four typical partitioning methods,and the optimal Louvain algorithm is used to identify urban space in this paper.Then it analyzes the constraints in the process of rail transit network generation,including the shape and layout of the rail transit network and the measurement of the scale of the network.In terms of online form and layout,this paper first expounds the factors of the shape of the net,followed by three typical net forms of the grid type,acyclic radioactivity and the ring-shaped radioactive wire network,as well as the ring layer,the dispersed group type and the strip type.The characteristics of urban spatial structure are introduced and adaptive analysis.In terms of online network size measurement,based on the existing length measurement method,a network of four factors including travel demand,line network service area coverage,regression analysis and regional economy is proposed.The comprehensive measurement method of length,followed by the collection of rail transit network and the multi-year operation of major cities in China,measured the non-linear coefficient of domestic rail transit and the average passenger flow intensity.These indicators will be an important constraint in the wire mesh generation process.Then this paper proposes a method for generating rail transit network based on network community structure.The method for generating the net network mainly includes two parts:urban space structure identification and line network layout.Firstly,based on the urban space passenger flow matrix,the Louvain algorithm is used to group the urban space and identify the urban spatial structure.According to the results of urban spatial structure division,firstly,the network solution space is generated between groups and within the group.The intermal network generation algorithm of the group mainly aims to meet the travel demand of residents,and the Dijkstra shortest path search algorithm and all have the full Based on the passenger flow allocation algorithm,the average passenger flow intensity of domestic rail transit and the non-linear coefficient of rail transit lines are used as constraints to determine the candidate rail sections within the group;and the layout of the network between groups is to meet the needs of urban development.Combined with the OD shortest path passenger flow distribution,the layout of the rail transit network adapted to the urban spatial structure is arranged;finally,the network between the inside of the group and the group is merged to form a preliminary network of rail transit,and the length of the rail transit network is used as a constraint.Make adjustments to form the final urban rail transit floor network.Finally,taking the domestic A city as a case study,the wire network generation algorithm method of this paper is applied to the rail transit network layout,and the formed network is compared with the network formed without spatial group division,based on the network community structure.On the basis of meeting the needs of residents' travel,the network pays more attention to the adaptability of the rail transit network and the urban spatial structure,strengthens the connection between the urban central area and the suburbs,and is of great significance for balancing the development between urban areas.