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Comparative Evaluation of Transportation Planning Methodologies for Florida's Evacuation Response - January 1997

Executive Summary
Significant progress has been made in the hurricane evacuation planning field in Florida and in other vulnerable coastal areas. These advances have produced a variety of methods for evaluating transportation aspects of hurricane evacuation. The overall goal of this project is to improve the transportation planning procedures used by Florida counties and Regional Planning Councils to perform hurricane evacuation analysis. This analysis yields forecast clearance times and other information regarding highway conditions and access to shelters. Consistency of transportation analysis is also important for studying evacuation scenarios for entire sections of the state of Florida.

This project was performed for the Department of Community Affairs, Division of Emergency Management, by Florida State University with assistance from Hall Planning & Engineering, Inc. Funding was provided by the Florida Emergency Management Preparedness and Assistance Trust Fund. Data collection techniques employed for this study included a "desk audit" of different transportation modeling methods, surveys of transportation practitioners and users and workshop discussion to identify key issues. A general study was performed on four regions within Florida with more detailed evaluation continued for the Treasure Coast Region and the Southwest Florida Region.

For the global review, a synopsis of current urban travel model structure is provided since the hurricane evacuation process is related to the planning for daily travel movements. The literature review determined that none of the techniques available nationwide were deemed more effective than several of the models currently in use in Florida.

After a brief review of hurricane evacuation planning in the Southwest Florida Region, Tampa Bay Region, Treasure Coast Region and the Withlacoochee Region, transportation modeling techniques used in the Southwest Florida and Treasure Coast Regions were examined further because they represent the top contenders for use in multi-region evacuation scenarios. The Treasure Coast methods were developed during projects performed by Post Buckley Schuh & Jernigan, Inc. for the U.S. Army Corps of Engineers. The technique used in the Southwest Florida Region was developed and applied by the Southwest Florida Regional Planning Council.

The method used by the Treasure Coast was initially developed for the Corps of Engineers during the Southeast Florida Hurricane Evacuation Study. This method is referred to in this document as the Lewis Model or Lewis Method in recognition of Donald C. Lewis and his more than 15 years of dedication to the field of hurricane evacuation planning. Mr. Lewis's successful career in this important field includes studies throughout the East Coast, Gulf Coast and Hawaii. His valuable work has led to numerous advances in the field.

After reviewing the Lewis method and the Southwest Florida methods, they were found to be quite similar in that they followed the basic stops of the transportation modeling process, were manually performed using computer spreadsheets, and made use of behavioral and storm surge data to perform the transportation analysis. The key difference was the inclusion of full trip table and traffic assignment steps for all roadway links in the Lewis method versus the partial assignment or corridor only assignments performed using the Southwest Florida RPC process. Although the corridor assignment approach appeared to work well enough for the geography of the Southwest Florida region, the more complete area wide traffic assignment technique was deemed important for accuracy across the wide variety of regions within the state of Florida.

The surveys of emergency management officials and transportation planners provided a clear image of their perceptions regarding the hurricane evacuation planning process. Overall, they were very satisfied with the hurricane evacuation studies, however, they pointed out distinct areas for improvement and sources of error in the process. These groups seemed quite concerned about the accuracy of population, dwelling unit and auto ownership data in vulnerable zones along the coast. A second concern centered on the behavioral surveys, their accuracy, frequency and reliability. Regarding the final product of these studies, the clearance time estimates, a large number of both the emergency management officials and transportation planners considered clearance time estimates to be within four hours of actual clearance times.

A main thrust of the study was to evaluate empirical data available regarding clearance times. It was found that actual measurements of clearance time were not available and that many analysts relied on anecdotal information from traffic control officers to document the end of hurricane evacuation traffic movement. The emphasis of the study, therefore, turned to the telemetry traffic count stations maintained by the Florida Department of Transportation (FDOT) as a primary source of evacuation traffic movement, direction and volume as well as duration of clearance time prior to storm arrival. Significant recommendations are made in this study that strongly suggest use of these counts by emergency managers during both studies and real time hurricane evacuation events. The full set of counters can provide a wealth of information regarding traffic congestion locations and duration of evacuation movements.

The two workshops, held on Lake Okeechobee in Clewiston, Florida which represented a midpoint between the Treasure Coast and Southwest Florida Regions, generated healthy discussion on many issues. The first workshop helped identify priorities for evaluation criteria as well as issues for consideration during this study. Face-to-face discussion was also helpful in the study team's understanding of many procedural details in the methodologies. The second workshop provided a forum for presentation of the major study findings. Immediate feedback was provided to facilitate refinement of the conclusions and recommendations. The workshops provided a very beneficial environment for discussing hurricane evacuation planning methods. This is the first time that the major proponents of two different evacuation transportation methods had come together in a relaxed forum to discuss the model differences as well as similarities. The greater understanding that resulted from these workshops should be a catalyst for continued forums of this type in the future.