Yongliang Deng

Topology Vulnerability Analysis and Measure of Urban Metro Network: The case of Nanjing

Urban metro network system is the most effective solution for relieving traffic congestion in large cities. With the development of metro, vulnerability analysis is a core process of metro safety management under the condition of network operation. In this paper, Nanjing planned metro network, in china, which was investigated and analyzed based on the graph theory complex network theory. The metro network topology characteristics and functional properties can be studied by Space L model. Several parameters were used to analyze and measure the topology vulnerability. The fraction of removed nodes is discussed and quantitatively compared in different protocols; meanwhile, the critical threshold of the fraction is 0.05-0.07. The study indicates that Nanjing planned metro network sharing some similar characteristics with those of scale-free network and small world network simultaneously; the metro network is robust against random attacks but vulnerable to malicious attacks; two parameters called global efficiency and average path length were proposed to measure the vulnerability of metro network. In the quantization of vulnerability, both betweens and degree need to be comprehensively considered, because parameter value and its influence are not absolutely positively correlated; In the end, a qualitative calculation method is proposed to calculate the node or vulnerability based on global efficiency and average path length.

Complexity and Vulnerability Analysis of Critical Infrastructures: A Methodological Approach

Vulnerability analysis of network models has been widely adopted to explore the potential impacts of random disturbances, deliberate attacks, and natural disasters. However, almost all these models are based on a fixed topological structure, in which the physical properties of infrastructure components and their interrelationships are not well captured. In this paper, a new research framework is put forward to quantitatively explore and assess the complexity and vulnerability of critical infrastructure systems. Then, a case study is presented to prove the feasibility and validity of the proposed framework. After constructing metro physical network (MPN), Pajek is employed to analyze its corresponding topological properties, including degree, betweenness, average path length, network diameter, and clustering coefficient. With a comprehensive understanding of the complexity of MPN, it would be beneficial for metro system to restrain original near-miss or accidents and support decision-making in emergency situations. Moreover, through the analysis of two simulation protocols for system component failure, it is found that the MPN turned to be vulnerable under the condition that the high-degree nodes or high-betweenness edges are attacked. These findings will be conductive to offer recommendations and proposals for robust design, risk-based decision-making, and prioritization of risk reduction investment.

Using Network Theory to Explore the Vulnerability of the Subway System

The subway has become the most effective form of transport for relieving traffic congestion in China. The vulnerability of the subway should be studied to improve the safety level in subway operation. In this paper, first of all, the general analytical method of systemic vulnerability was expatiated thoroughly. Then, the centrality theory was introduced to analyze the subway equipment system network (SESN). Next, an undirected SESN was established based on in-depth analysis of the subway system. In the end, based on SESN, vulnerability of the subway was identified by aid of PAJEK and R software platform. The study indicated that the critical vulnerability of the subway system is optical fiber system and automatic train supervision system, and there is a strong positive correlation between the vulnerability and the centrality.