Wildlife-vehicle collision (WVC) causes direct mortality and reduces population connectivity. Although the idea of WVC is well-characterized, its total impact on wildlife populations remains poorly understood. Here, we describe a method for estimating the impact of WVC at the US state scale, with a case study on California mule deer (Odocoileus hemionus). We used GenEst (USGS) (Dalthrop et al., 2018) to fit models, which incorporates rates of carcass observation, persistence, and effort, taken from our data collections systems, and search efficiency, from the literature. Our models were constrained by habitat suitability and split into categories by: traffic volume, bioregion, and year and season. Rates of deer-vehicle collisions (DVC) were estimated for each category using 43,021 observations of DVC between 2016-2023. We find region-variable rates, between 0-1.4 DVC/km (South Coast) and 0.4-5 DVC/km (Sierra Nevada/Modoc). We estimated that 34,000 to 53,000 mule deer were killed per year. This represents about 10% of the estimated statewide population, suggesting WVC may play an important role in its steady decline. Our approach is readily applicable to other populations with sufficient data collection, which we are carrying out for other CA species.