| Urban rail transit system(URTS)has significantly alleviated traffic congestion,reduced traffic accidents and improved air quality depending on its outstanding characteristics of large transport capacity,high speed,good punctuality,high safety and low pollution,which not only has been favored by the authority of metropolis,but also has become an important means to solve "urban diseases",such as traffic congestion,traffic accidents and environmental pollution.It can be seen that urban rail transit is the only way to realize the green,low-carbon and highquality development of urban transportation.From the perspective of operation process,URTS has the characteristics of concentrated ridership distribution,limited station space,closed operation management,and narrow access to the station.In case of an emergency or accident occurred,it is easy to lead to property losses and casualties.Therefore,how to avoid the occurrence of urban rail transit operation events or accidents and restore system operation as soon as possible after such events or accident occur,have always been an important issue of concern to the Central Committee of the Communist Party of China and the government,and an important task for the urban rail transit operation management department.From the perspective of complex network,this paper proposes the research approach based on “constructing the topological structure model of urban rail transit ——analyzing the evolution process of network structure— —Interpreting the spatio-temporal distribution characteristics of network ridership——analyzing the invulnerability of network cascading failures——assessing the network resilience”.To be specific,this paper studies the structural evolution mechanism of urban rail transit network(URTN),analyzes the spatio-temporal evolution characteristics of ridership,systematically assesses the invulnerability of URTN,and investigates the resilience and recovery strategies of URTN.Firstly,the paper studies the structural evolution characteristics of URTN.The distance weighted URTN topology model is constructed using the Space-L method,and five indicators,including average path length,network diameter,network efficiency,betweenness centrality,and closeness centrality,are further redefined.Twelve indicators,such as the number of stations,the number of edges,the operating mileage,the weighted average path length,the weighted network diameter,the weighted network efficiency,the network connectivity index,the network meshedness index,the average degree,the average weighted betweenness,the average weighted closeness,and the average eigenvector vector centrality,are preliminarily selected as the basis for dividing the network evolution stages.The network evolution stage division method of URTN based on the Gaussian mixed model(GMM)method is proposed.The URTN in Xi’an from 2011 to 2025 is divided into three stages: the initial stage(2011-2017),the development stage(2018-2023),and the mature stage(2024-2025).The overall evolution characteristics,network structure evolution characteristics and node centrality evolution characteristics of URTN in Xi’an in different evolution stages are discussed respectively.Secondly,the paper analyzes the spatio-temporal evolution characteristics of ridership in URTN.The characteristic years of the initial and development stages are 2017 and 2021 are selected respectively,and the inbound and outbound records of smart cards from May 15-21,2017 and July 5-11,2021 are obtained.From two levels of network and lines,the temporal distribution characteristics of inbound and outbound ridership on weekdays and weekends in2017 and 2021 are analyzed,and the influence of URTN mileage increase on ridership temporal distribution is analyzed.From the station level,the spatial distribution characteristics of ridership of URTN in Xi’an in 2017 and 2021 are analyzed and compared,and the impact of the expansion of URTN in Xi’an on the spatial distribution of ridership is also analyzed.Thirdly,the paper explores the invulnerability of URTN under the influence of ridership.The space-L method and station ridership are used to construct a passenger-weighted topological structure model of URTN.The initial load and capacity of all stations are determined by the station ridership,and a comprehensive evaluation index of invulnerability,called transport efficiency,is proposed,which considers both the network topological structure and service quality.The change of network transport efficiency after attacking a single station is analyzed to identify key stations of the network.Meanwhile,the changes of the transport efficiency of the URTN with random and intentional attacks on multiple stations are developed under the three load distribution strategies,namely degree centrality distribution,betweenness centrality distribution and residual capacity distribution.URTN in Xi’an in the initial stage(2017)and the development stage(2021)are taken as an example for empirical analysis.Finally,the paper investigates the resilience assessment method of URTN.Considering network topology structure and service quality,this paper proposes a network performance response function,which is the weighted sum of OD ridership loss rate and network service efficiency loss rate.The composite weight of indicators is determined by the Delphi-entropy weight method.A resilience assessment method based on network performance response function is proposed,and four hypothetical perturbance scenarios are constructed.Three recovery strategies,including random recovery strategy,preference recovery strategy,and target recovery strategy,are utilized to analyze the recovery effect of URTN resilience.Taking URTN in Xi’an in the initial stage(2017)and the development stage(2021)as an example,this paper compares and analyzes the the differences between the target recovery strategy,the random recovery strategy and the preference recovery strategy on the network resilience repair effect under four hypothetical perturbance scenarios.The sensitivity analysis method is applied to explore the impact of different repair resources on the network recovery.This paper studies the structureal evolution process of URTN from the perspective of complex networks,and analyzes the impact of different network sizes and structures on the spatio-temporal distribution of ridership.The operation safety management level of URTN is improved and enhanced through the research on invulnerability and resilience of URTN,which contribute to in-depth understanding of the stability of URTN and provide the theoretical support for urban rail transit operation management departments to develop safety protection strategies and emergency rescue plans. |
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