Transportation infrastructure can restrict wildlife movement and increase wildlife-vehicle collisions (WVCs) that kill over 48,000 deer in California annually. Medians, which separate opposing traffic lanes, vary in type (e.g., concrete barriers, metal guardrails, vegetated strips) and may influence WVC rates. At Caltrans' request, we assessed the impact of median types on WVC rates along California highways. Using Google Street View, we categorized median types at 1,069 mule deer (Odocoileus hemionus) WVC sites in Caltrans District 9 and 332 western gray squirrel (Sciurus griseus) WVC sites in Caltrans District 2 between January 2015 and April 2024. Chi-square tests showed significant differences between WVC site medians and randomly generated site medians, suggesting that median type affects WVC density for both species. Additionally, we analyzed 73 paired highway transects where the median transitions from one type to another, comparing WVC rates along 1-mile stretches. Wilcoxon tests revealed WVC rates were 1.95 times higher along metal guardrails than vegetated strips (p=0.045), though other pair comparisons were not significant. These findings highlight the influence of median treatments on WVCs and suggest that transportation planning should consider wildlife connectivity impacts to reduce collisions.

Ben Hodgson is a Geospatial Data Analyst at the UC Davis Road Ecology Center. After earning his undergraduate degree in environmental planning from UC Davis in 2024, Ben took on a role focused on developing GIS solutions to support research at the intersection of transportation infrastructure and wildlife. His work examines how roadways affect animal behavior and populations, aiming to inform strategies that mitigate the impact of infrastructure on wildlife.