Vulnerability Identification of Urban Road Network under Unexpected Congestion

An original method is used to analyze the topology structure of a road network and two indexes of road network performance, namely, connectivity and network efficiency, are used to evaluate road network robustness in medium measure and thus quantify the variety of urban road network vulnerability caused by unexpected congestion. Then, a variety of road network impedances is set as the vulnerability identification index and a network traffic flow model with a link queuing capacity constraint is established, considering such constraint on unexpected congestion condition. Finally, a Lagrange dual algorithm is designed to solve the model, whose accuracy is subsequently tested by an example. Results show that the model based on the vulnerability index can accurately recognize road network vulnerability. Invalid links caused by unexpected congestion lead to changes in road network impedance, thereby directly affecting the robustness of the entire road network.