Critical Link Analysis for Urban Transportation Systems

Abstract

A fundamental and important step for safety analysis for an urban transportation system is to find its critical links. However, most approaches in the current literature focused on highway or intercity transportation systems. The key characteristics of urban transportation systems were not considered and the concept of criticality of links was mixed up with the concept of vulnerability. This paper defines the criticality of links from two perspectives, i.e., the vulnerability and potential, based on which a novel methodology for identifying critical links in an urban transportation network is proposed. This novel methodology includes a ranking method and a novel mesoscopic model to examine the urban transportation network performance. The mesoscopic model is a novel cell transmission model, which grasps key characteristics of an urban transportation network, such as dynamic demand generated on links, different link lengths, and intersection flow assignment. The method is validated by a real world case from Hong Kong. The simulation results indicate that the ranking of critical links depends on particular scenarios, available resources, and both supply and demand of the system; furthermore, two paradoxes are discovered and discussed.