Network Robustness Index: A new method for identifying critical links and evaluating the performance of transportation networks

Highway planning efforts, especially those involving capacity expansions, have traditionally relied on the volume/capacity (V/C) ratio to identify “highly congested” or critical links, resulting in localized solutions that do not consider system-wide impacts. This paper presents a new, comprehensive, system-wide approach to identifying critical links and evaluating network performance. The approach considers network flows, link capacity and network topology. Moreover, it relies on readily available sources of data. Using three hypothetical networks, we demonstrate that the approach, known as the Network Robustness Index, yields different highway planning solutions than the traditional V/C ratio. Moreover, these solutions yield far greater system-wide benefits, as measured by travel-time savings, than solutions identified by the V/C ratio.