The vulnerability is a good indicator to reflect the road capacity. However, most of previous researches mainly concentrate on the vulnerability modeling in critical link and analyzing with simulated topological road network. For trying to fill these gaps, this study proposes a new methodology for evaluating vulnerability of urban road network based on the concept of macroscopic fundamental diagram (MFD). This measure is derived by comparing the behavior of the MFD under actual conditions with that under theoretical conditions, while the Real-time Vulnerability Index (RVI) that enables real-time measurement and monitoring of road vulnerability is calculated as a sliding average per hour. Using empirical data from Shanghai expressway, we demonstrate the applicability and validate of the proposed method in real traffic scenarios. It is also confirmed that the RVI is also effective in reflecting spatial characteristics such as bottlenecks or traffic congestion on the road in real time once they occur on the index. The index is therefore well placed to provide management advice to road management authorities.
 

Macroscopic Fundamental Diagram;Vulnerability;Urban Expressway