Research On Optimization Model And Algorithm Of Urban Emergency Network Construction

Urban rail transport has many advantages,such as high capacity,clean power,punctuality and no traffic congestion,which makes it an important part of the urban transport network.By the end of 2021,a total of 50 urban rail systems had been built in mainland China,with a total length of 9,206.8 km,providing convenient services for residents to travel.In these cities,78.3% of the rail lines were operational,compared to 21.7% for other types of rail lines.In addition to this,the total length of the new lines in operation reached 1,237.1kilometers.According to statistics,there are 24 cities in the country with at least four rail lines with three or more interchange stations,which brings the rail coverage in these cities to 48%.the cumulative number of passenger trips completed in the year 2021 was 23.69 billion,an increase of 34.7% year-on-year,the total number of station entries was 14.63 billion,an increase of 33.7% year-on-year,and the total passenger turnover was 198.18 billion passenger-kilometers,an increase of 33.3 per cent year-on-year.Urban rail transit and bus networks are the two main transportation modes in urban transportation networks,and they play a key role in providing emergency services.To establish an efficient urban emergency network,it is essential to optimize the structure of the urban rail transit and bus networks.With the continuous expansion of the urban rail transit network and the increasing number of emergencies,the possibility of station failure and shutdown increases,which may trigger cascading failures throughout the network.Therefore,there is an urgent need to establish an optimized model and algorithm for constructing an urban emergency network.The main research results of this paper are as follows:(1)This paper aims to explore the construction optimization model and algorithm of the urban emergency network to improve the network efficiency and robustness of the urban emergency network.Based on the theory of complex networks,the research objectives of this paper are to explore the path selection and traffic flow dynamics of the urban emergency network,and to study the cascade failure evolution.Our research aims to use the current network characteristics and changes in passenger behavior to determine the best network structure,prevent large-scale cascading failures of the urban public transportation network,and formulate key defense strategies for node cascading failures.The introduction of complex network theory can better understand the complexity and multi-level nature of the urban emergency network,which helps to construct more accurate models and algorithms.Through the results of this study,we can improve the robustness and network efficiency of the urban emergency network,and better play the role of urban emergency functions in responding to emergencies.(2)This paper aims to coordinate and optimize the traffic flow of the urban emergency network.Firstly,by constructing a two-layer complex network model of the urban emergency network,the nodes and edges in the network are accurately described,and their structure and characteristics are analyzed.Based on this,a path selection algorithm and traffic flow dynamics are proposed to achieve coordinated optimization of the urban emergency network.For the stations in the urban emergency network,this study proposes a new node importance evaluation method,which combines the K-shell decomposition method and composite weight assignment.By establishing the emergency network of Tianjin City,this study applies the proposed method to optimize the network structure and verify the effectiveness of the method.This urban emergency network coordination optimization method based on the two-layer complex network provides new ideas and methods for the construction and optimization of urban emergency networks.(3)This article proposes a new model that considers the direction of passenger flow in nodes and achieves effective control of urban rail transit networks when facing attacks through a two-layer complex network mechanism.Compared with traditional methods,the model in this article is more refined and comprehensive,not only considering the objective factors of node failure,but also fully considering the subjective choices of passengers after node failure,thus more realistically simulating the evolution process of urban rail transit networks.At the same time,the model proposed in this article can also adjust the optimal loading direction for different directional passenger flows,making the passenger load of the network more balanced,and improving the network’s robustness and stability.Finally,the model is verified through examples by simulating the Tianjin rail transit network under different scenarios,and the cascading failure evolution under different situations is obtained.These results help us to have a deeper understanding of the microdynamic process of urban rail transit networks when facing attacks and provide scientific basis for formulating corresponding emergency measures.