Transit-Based Emergency Evacuation Simulation Modeling

Abstract

Several recent mass evacuations, including those in advance of Hurricane Katrina in New Orleans and Hurricane Rita in Houston, have demonstrated the effects of limited planning for carless populations. The lack of planning left a significant portion of the mobility-limited population of both these cities unable to flee in advance of the storms. Since 2005, however, both of these cities (as well as others across the United States) have developed transit-assisted mass evacuation plans at various levels of detail. Because these plans are relatively recent and do not have a history of experience on which to base their performance, it is difficult to know how well, or even if, they will work. This article describes one of the first attempts to systematically model and simulate transit-based evacuation strategies. In it, the development of and the results gained from an application of the TRansportation ANalysis and SIMulation System (TRANSIMS) agent-based transportation simulation system to model assisted evacuation plans of New Orleans are described. In the research, average travel time and total evacuation time were used to compare the results of a range of conditions over a two-day evacuation period, including two alternative transit evacuation routing plans and four alternative network loading scenarios. Among the general findings of the research was that the most effective scenarios of transit-based evacuation were those that were carried out during time periods during which the auto-based evacuation was in its “lull” (nonpeak/overnight) periods. These conditions resulted in up to a 10% reduction in overall travel time and up to 45% reduction in the total evacuation time when compared to peak evacuation conditions. It was also found that routing buses to alternate arterial routes reduced the overall travel time by up to 52% and the total evacuation time by up to 14%.