Emergency Planning in the Urban-Wildland Interface: Subdivision-Level Analysis of Wildfire Evacuations

Abstract

This project was motivated by recent research that has advocated the need for a better understanding of and planning for evacuations of residential subdivisions under threat from wildfires. Prior work has suggested that the density of housing units and ineffective evacuation routing and egress may have contributed to fatalities in subdivisions in which residents were unable to evacuate when the need arose. To evaluate the effects of development density and street network layout, this study utilized simulation to represent and evaluate various evacuation scenarios at the neighborhood level under ranges of housing density and threat urgency. The results of this study illustrate the relationships between the traffic that can be accommodated by a roadway network; the location and number of egress points; and the time during which vehicles enter and exit the network. Most significantly, it showed how changes in traffic volume need to be accompanied by corresponding increases or decreases in time and/or egress capacity to move evacuees out of the threat zone. Similarly, changes in the network (i.e., adding and/or modifying the location of exits) were also shown to significantly decrease evacuation clearance times and increase the total exiting traffic.