Environmental factors affecting the frequency and rate of deer-vehicle crashes (DVCs) in southern Michigan

Deer vehicle collisions (DVCs) are a major economic and social problem in Michigan. The aim of this research was to better understand environmental factors affecting the frequency and rate of DVCs and to develop models that predict DVC occurrence. The study area comprised of Monroe, Washtenaw, and Oakland counties in southeastern Michigan. A random sample of 450 DVC and 450 non-DVC points along roadways was selected within each county. Information regarding road class, number of lanes, traffic volume, speed limit, habitat suitability, and dominant landcover was built into each point. Contingency tables comparing DVC to non-DVC points were generated and relative risk calculated. Based on a conceptual model of DVCs 8 a priori models of DVCs were evaluated. The order of importance of causal factors (highest to lowest) of DVCs was habitat suitability index, traffic volume, and speed. Relative risk between DVC and non-DVC locations for all 3 counties was higher on rural roads than urban roads, and on roads with traffic volume > 120 vehicles/hr than ≤ 120 vehicles/hr. High speed roads with > 2 lanes had the highest relative risk in Monroe County whereas medium speed roads with > 2 lanes had the highest relative risk in Washtenaw and Oakland counties. Vegetation management that involves planting low quality forage along roadways for deer may be most helpful in reducing number of DVCs. Actions that reduce traffic volume or speed in moderate quality habitats for deer will result in fewer DVCs. High speed, high volume roads in urban landscapes may become a barrier to deer.