The impact of wildfire smoke on traffic evacuation dynamics

This study investigates how reduced visibility due to wildfire smoke affects driving behaviour, specifically speed and headway, and the resulting implications for evacuation management and planning. Data were collected from participants immersed in a virtual environment through a driving simulator with a head-mounted display. Thirty-seven participants drove through scenarios simulating a rural highway. While driving visibility was systematically varied with virtual wildfire smoke. Participants were initially alone on the road to measure freeflow speeds and then proceeded to drive behind a convoy of cars. When visibility was low, driving speed was significantly reduced compared to the scenario with unrestricted visibility. Surprisingly, however, participants maintained similar distance headways in denser smoke compared to conditions with unrestricted visibility, suggesting that car-following behaviour was not affected. The collected data were used to develop a model that captures drivers' responses to reduced visibility due to smoke. The proposed model can be integrated into both macroscopic and microscopic traffic models, providing a tool for estimating evacuation times.