Research On Evolutionary Characteristics And Localized Vulnerability Of Subway Networks

The subway systems in China have been extensively constructing througout the whole country in recent years,and in the end of 2020 there will be around 40 cities with subway systems.Constructing these systems has also been doubted by stakeholders.First,whether it is necessary for some cities to construct subway systems or new subway lines? Second,how to better plan subway systems? Whether planning new subway systems or new subway lines can be inspired by the evolutionary processes of those large-scale mature subway systems? Also,subway systems are subject to various types of hazards,such as earthquakes,floods,fires and terrorist attacks,some of them can cause the localized damage,then how to analyze the vulnerability of subway systems under those localized attacks? To address the above problems,this thesis uses the correlation analysis method to uncover the relationships between subway systems and urban development in China,analyze the similarities and diversities of subway systems in different cities and study the subway system vulnerability under spatially localized attacks.By conducting the correlation analysis between subway growth and many other urban indicators,such as population,GDP and traffic congestion level,respectively,it indicates that the increase of urban population and GDP can significantly faciliate the construction of subway systems.By analyzing the evolutionary characteristics of subway networks in different cities,it is found that these subway networks show similar evolutionary rules: the first subway line in most of cities passes through the city center,and most of the subway lines passes through an area within five kilometers of the city center.According to those indicators for the evolutionary characterstics of subway networks in different cities,it can divide the evolution process of a typical subway network into three stages: rapid growth stage,stable expansion stage and mature stage,in each of these stages,those indicators which describe the evolutionary characteristics have similar values.By adopting the circle shaped localized attack mode,it enables computing the worst-case localized vulnerability and identifying the critical area in a subway system for protection.Taking the subway network in Wuhan as example,it is found that under the localized attack with a radius of five kilometers,system vulnerability(between 0 and 1)can reach 0.7,impacting seven of all nine subway lines in this city;also,with the increase of the attack radius,the critical area for protection moves from subway line one near the north bank of the Yangtze river to subway line four near the south bank of the river,with the center of the critical area gradually moving towards the barycenter of the city.In addition,by comparing the localized vulnerability of subway networks in Beijing,Shanghai,Shenzhen,Guangzhou,Xian and Wuhan,it shows largely different results,with the vulnerability for Xian around two times the vulnerability for Beijing under an attack radius of five kilometers.