Traffic Impacts and Dispersal Patterns on Secondary Roadways during Regional Evacuations

Abstract

The evacuation of southeast Louisiana in the days prior to Hurricane Katrina represented the largest concentrated movement of traffic in the history of the state. Traffic data showed that nearly a half million vehicles, carrying an estimated one million people, flowed out of the New Orleans area before the storm. Since it was well recognized that evacuation traffic would overwhelm the available network capacity, Louisiana transportation and state police officials developed a plan to achieve a maximum utilization of the state’s highest capacity evacuation routes. This paper differs from prior analyses by shifting the focus of attention from the impact of evacuation traffic on freeway and primary arterials to secondary and low volume roadways that have historically been underutilized during such emergencies. Analyses were conducted to determine how traffic was dispersed on the secondary roadway network, how long the impacts lasted, and where they were the most pronounced. The results suggest that many Katrina evacuees used roads in the secondary system as their primary routes of egress to far greater degrees than previously thought. They also indicate that secondary and low volume routes were also well used as alternatives to saturated interstate freeways and by evacuees seeking destinations not directly served by the primary highway network.