Investigating Reliability Of Urban Rail Transit Networks By Means Of Complex Network Theory

The fast-increasing travel demand in medium-and large-sized cities in China has put the governments at various levels under huge pressure to mitigate the ever-worsening traffic congestion and pollution problem. To address this problem, a huge amount of effort and capital has been invested in planning, constructing and improving urban public transit systems. In this process, a main trend is the large-scaled construction of urban rail transit systems across the country because the systems of this kind possess a range of advantages over bus transit systems, including high speed, high capacity, high reliability, security, punctuality, and also comfort. On another hand, under the influence of more and more complicated social environment (e.g. more and more malicious human acts) and inevitable and unpredictable natural disasters (e.g. floods, earthquakes), the reliability of urban rail transit networks has received more and more attention both from the governments and from the academia.In recent years, the subject of complex networks (or network sciences) has achieved a great progress, either in theory or in application. To use the complex network theory to investigate the reliability of urban rail transit networks is a big step forward. Traditionally, the focus of research on transit networks is on passenger capacity, turnover capacity and average travel distance and so on, which, however, did not pay enough attention to network structures. This has negatively affected the further improvement in the reliability of transit networks. This thesis aims to fill this gap and investigates the reliability of urban rail transit networks by focusing on network structures by means of the theory of complex theory. For this purpose, a series of evaluation indices have been proposed, including the largest connected subgraph and global/local network efficiency; by observing the values of these indices, the planner can identify ways to enhance the existing structures and management of a urban rail transit network, which can improve the reliability of the network.As the applications of this research, this thesis analyzes the reliability of the three Shenzhen rail transit networks that have been planned respectively for2011.2016and2030. First, we present the characteristic indicators of these rail transit networks with a comparative analysis. This analysis shows that the connectivity of the2030-oriented Shenzhen rail transit network should be improved to enhance the reliability of it. Then, we investigate the reliability of the2011-oriented Shenzhen rail transit network. The first step is to evaluate the reliability of the network:we assume that two types of attack behavior may take place, i.e. random attacks and intentional attacks. This investigation shows that the network has an obvious scale-free network characteristic, which means a strong network robustness while facing random attacks but certain vulnerability if an intentional attack occurs.Once more, we investigate the contribution of a bus network in a city to the reliability of the urban rail transit network in the same cily. Again, we apply our method to the Shenzhen rail transit networks and find out that a well-planned bus network can make up the shortcomings born from birth of an urban rail transit network, such as requirement of huge amount of investment, restricted curvature of each line, and low coverage density across the city, and so forth. Conventional bus networks can enhance the network characteristics, in particular reliability, of urban rail transit networks. Last but not least, we take into account the impacts of travel demand and its distribution on the network reliability and rank the importance of network nodes.It can be concluded that the method and analysis given in this thesis may benefit the theoretical investigation and management of rail transit network reliability and security.