Development of a Strategic Hurricane Evacuation-Dynamic Traffic Assignment Model for the Houston, Texas, Region

This paper describes a hurricane evacuation model for the Greater Houston, Texas, area whose base case reproduces the widespread congestion and gridlock experienced during the evacuation response to Hurricane Rita in 2005. The project-a result of the combined efforts of the Houston-Galveston Area Council (H-GAC), the Texas Transportation Institute (TTI), and Citilabs-incorporated the development of a dynamic traffic assignment model for evaluating the performance of major evacuation routes within the H-GAC region. To minimize model run time while maximizing policy analysis capabilities, a strategic model was developed on the basis of the full H-GAC regional model network and zone system. This strategic model integrates tightly with the regional planning model and can be updated with new information concerning the structure of background demand derived from normal weekday trip tables. Evacuation trip tables were developed by TTI based upon survey data collected shortly after the 2005 event. In the network assignment model, background and evacuation trips are incrementally loaded by using a dynamic, generalized cost framework that can be modified to account for route preference, traveler information, transportation supply dynamics, and congestion feedback over a 72-h model period. Policy analysis tools provided with the model include supply-side controls such as contra-flow lane reversal timing, facility closures, incident response, as well as demand-side controls such as evacuation trip departure scheduling. The model can be applied to comparison of the relative system and evacuation corridor performance of alternative policy scenarios.