Estimation of Road Capacity in Case of Disasters by Incorporating Simulation and Bottleneck Concepts

Degradation of transportation networks accounts for a considerable amount of damages incurred as a result of disasters. Capacity, as one of the fundamental characteristics of roadways, may be diminished in the aftermath of disasters. Hence, this paper aims to evaluate and estimate road capacity reduction with regard to different intensities of damages to the freeways and highways after disasters. Approaching the issue by simulating post-disaster conditions, it is assumed that road disruption can be modeled as a bottleneck resulting in capacity reduction. Due to the probabilistic essence of disasters and uncertainty of their temporal and spatial dimensions, one rational way to simulate post-disaster conditions is scenario planning. In this research, considering the closure of part of road width as a bottleneck, the flow through bottleneck is calculated by taking average of flows resulted from five simulation tests. Post-disaster capacity is considered as a function of base capacity and roadway/shoulder characteristics. The coefficient of remained capacity is then calculated as the ratio of the bottleneck through flow to the base capacity. Results indicate that capacity reductions are as capacity drops and is concluded that the more the number of lanes, the less the capacity drops. Moreover, the less the number of lanes, the faster and more severe the drops occurs.