Effects of Wildlife Warning Reflectors (“Deer Delineators”) on Wildlife-Vehicle Collisions in Central Wyoming

The purpose of this study was to provide the Wyoming Department of Transportation with information about (1) the effectiveness of Streiter-Lite wildlife warning reflectors that had been installed in three locations within Wyoming’s District 5, and (2) preliminary analysis of patterns of deer-vehicle collisions across Wyoming and the habitat and road variables associated with collision hotspots. The authors evaluated reflector effectiveness in terms of their ability to reduce deer-vehicle collisions and modify deer road-crossing behavior. Using a series of experimental manipulations of reflectors, the authors showed that reflectors reduced deer-vehicle collisions by 32 percent and significantly reduced the number of high-risk deer road crossings (those in which deer ran into the road as a car was approaching). However, covering reflectors with white canvas bags – initially done with the intent of creating a control treatment that neutralized the reflectors – proved even more effective than leaving the reflectors exposed. White bags on posts resulted in 33 percent fewer collisions than when reflectors were exposed and significantly reduced the number of high-risk deer road crossings. It is likely that the white bags are more visible or reflective to deer than the red wildlife warning reflectors. A cost-benefit analysis suggests that the benefits of reflectors outweigh their initial materials and installation costs, but may not outweigh the net costs once maintenance is taken into account. Analysis of patterns of deer-vehicle collisions across the state showed that traffic volume, proximity to agricultural land, proximity to deer winter range and migration routes, and high speed limits are all strongly associated with high collision rates. On average, areas with a 55 mph speed limit have 36 percent and 55 percent fewer deer-vehicle collisions than areas with speed limits of 65 and 75 mph, respectively. Reducing nighttime speed limits in high collision areas may be a cost-effective strategy for mitigating deer-vehicle collisions in Wyoming.