Nighttime Traffic Volume Predicts Risk of Deer–Vehicle Collisions

Annually, in the United States, \u3e1 million deer (Odocoileus spp.)–vehicle collisions are reported, resulting in losses of $4.6 billion in vehicle damage and medical expenses. Wildlife and transportation managers require better information about traffic volumes relative to seasonal and diurnal deer movement patterns to appropriately evaluate the risks associated with deer–vehicle collisions (DVCs). We incorporated traffic volume data with DVC data and the movement rates and incidences of road crossings by white-tailed deer (O. virginianus) to evaluate if traffic volume or deer behaviors mediate the incidence of DVCs along a high-volume interstate highway in Morgan County in central Georgia, USA. From May 2012 to July 2014, we monitored the movements and survival of 25 deer (13 males, 12 females) instrumented with global positioning system (GPS) collars in an area 1.6 km north and south of a 7.7-km section of Interstate 20 in our study area. We used a linear mixed model to quantify the effects of mean traffic volume and total road crossings on DVCs for each hour of the day. Deer movements and DVCs were primarily crepuscular. Approximately 60% of GPS-collared deer crossed roads; 7 deer accounted for \u3e90% of all road crossings. Approximately 73% of daily traffic occurred between 0700 and 1859 hours. Nearly twice the number of daily DVCs occurred during the fall (9.8 DVCs/day) than during the next highest season (winter; 4.9 DVCs/day). Although DVCs occurred at greater frequencies during crepuscular periods, results of our linear mixed model suggested only nighttime traffic volume predicted DVCs. The relationship between nighttime DVCs and traffic volume is likely due to the inability of drivers to perceive deer in a roadway during this time. We recommend mitigation efforts focus on increasing driver vigilance and reducing vehicle speed during nighttime periods, especially during the fall season