A New Method For Calculating Network Robustness Index (NRI) In Urban Transportation Networks

Wide range of short-term destructive events like hurricanes, floods, fogs, fatalities and accidents occur every day in transportation network and have negative effects on thenetwork. The purpose of this study is to discuss such accidents and investigate the effects of them on the network which is implemented by Network Robustness Index. Network robustness is proposed recently in transportation scope and is an up-to-date issue in transportation investigations. Robustness is in contrast with network the concept of vulnerability, i.e. by increasing the robustness of network, vulnerability would decrease. In this study, traffic maps were analyzed by PTV-VISUM software and Arc GIS program, and travel-cost related to each link were determined by: travel-time, Peak Hour Volume (PHV) and link length, then the most important link of network was determined by all-ornothing assignment method and shortest-path-trees were plotted by MATLAB codes which was based on dijkstra algorithm and the cited link was called critical link. Critical link is the one which eliminating of that-in comparison to other links- leads to the most increase in travel-cost. Then, assuming a disruption to this link, maximum network robustness index was measured by calculating the difference of travel cost before and after disruption to critical link. In this investigation principal and minor arterial roads of BOJNURD city were considered as case study. Results showed that the PJ link is the critical link in the studied network; hence, by assuming disruption to this link, maximum network robustness is calculated.

Keywords:

Network Robustness Index , Urban Transportation Network , Vulnerability Assessment , All-Or-Nothing Assignment , Short-term Disruption , Critical Link