U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



DeVault, T. L., T. W. Seamans and B. F. Blackwell. 2020. Frontal vehicle illumination via rear-facing lighting reduces potential for collisions with white-tailed deer. Ecosphere 11(7):e03187. 10.1002/ecs2.3187


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nimal–vehicle collisions cause many millions of animal deaths each year worldwide and present a substantial safety risk to people. In the United States and Canada, deer (Odocoileus spp.) are involved in most animal–vehicle collisions associated with human injuries. We evaluated a vehicle-based collision mitigation method designed to decrease the likelihood of deer–vehicle collisions during low-light conditions, when most collisions occur. Specifically, we investigated whether the use of a rear-facing light, providing more complete frontal vehicle illumination than standard headlights alone, enhanced vehicle avoidance behaviors of white-tailed deer (O. virginianus). We quantified flight initiation distance (FID), the likelihood of a dangerous deer–vehicle interaction (FID ≤ 50 m), and road-crossing behavior of deer in response to an oncoming vehicle using only standard high-beam headlights and the same vehicle using headlights plus an LED light bar illuminating the frontal surface of the vehicle. We predicted that frontal vehicle illumination would enhance perceived risk of deer approached by the vehicle and lead to more effective avoidance responses. We conducted 62 vehicle approaches (31 per lighting treatment) toward free-ranging deer over ~14 months. Although FID did not differ across treatments, the likelihood of a dangerous deer–vehicle interaction decreased from 35% of vehicle approaches using only headlights to 10% of vehicle approaches using the light bar. The reduction in dangerous interactions appeared to be driven by fewer instances of immobility (freezing) behavior by deer in response to the illuminated vehicle (n = 1) compared with approaches using only headlights (n = 10). Because more deer moved in response to the illuminated vehicle, road-crossing behavior likewise increased when the light bar was on, although these road crossings primarily occurred at FIDs > 50 m and thus did not increase collision risk. Road-crossing behavior was influenced heavily by proximity to concealing cover; deer only crossed when the nearest cover was located on the opposite side of the road. We contend that frontal vehicle illumination via rearfacing lighting has potential to greatly reduce vehicle collisions with deer and other species. Future work should explore fine-tuning the method with regard to the visual capabilities of target species.