Road network topology vulnerability analysis and application

The performance degradation of a road network is determined by the network's vulnerability to incidents. When some links become unavailable after incidents, the connectivity of the network may be destroyed. As the connectivity of the network is always determined by its topological structure, the vulnerability of the road network topology structure was investigated. A vector-formed index was proposed to quantify the network's topology vulnerability. This index could be used to compare different networks, so it could become a useful tool for planners in comparing and selecting schemes. The value of the cardinality of the vector indicates the number of link sets, whose unavailability could destroy the connectivity of the network. A greater value indicates a more vulnerable network. Based on the network's topology vulnerability index, the criticality index of links can also be calculated. A larger criticality index for a link means a more critical link. Therefore, identifying critical links in a network is important for planning, and more emergency reaction resources should be allocated to these critical links. The result of a trial network shows the monotonicity of a link's criticality and a network's topology vulnerability. The Shanghai freeway network was tested as an application example. Its topology vulnerability was evaluated, all links were ranked, and the construction sequence of three planning schemes was proposed. Finally a discussion about the theory and application is presented.