Demand variations and evacuation route flexibility in short-notice bus-based evacuation planning

The output of the models devised for bus-based evacuations often only provides the time required to complete the evacuation with known input resources along with the routes for each bus trip. The different techniques used to minimize the evacuation time aim to improve either the demand or the supply side of the mechanism. Great care must be exercised to avoid negative impacts of such improvement efforts. In this study, two important factors, variation in demand and evacuation route flexibility, are discussed with respect to their effects on the optimality of bus-based evacuation planning. The model of short-notice bus-based evacuation under dynamic demand conditions (SBED model) was used to highlight the importance of these factors in evacuation planning through a case study of Kawajma Town. The model was run to simulate different evacuee demand and bus route scenarios, and the results were analyzed. In terms of the number of evacuees, better results were observed in the fixed-demand case than in the continuous-demand case. In addition, the results indicate that introducing evacuation route flexibility into the model reduces resource use but necessitates more model run-time.