Deer-vehicle crashes: extensive peak at 1 hour after sunset

On-road encounters with animals resulted in 231 fatalities in the United States in 1999, and the annual number of deer-vehicle crashes (DVCs) has been estimated to total more than 500,000. Previous studies suggest that the number of DVCs is highest during the hours of dusk and dawn. However, these studies have not adequately taken into account the synchronization of visibility and animal behavior with sunset and sunrise. The goal of this study was to determine the temporal variation in the crash risk, so that this variation could be better taken into account by road users.

In Finland, the recorded times for 13,379 crashes with moose and 8191 crashes with white-tailed deer were adjusted to sunset and sunrise according to the location and date of occurrence. In addition, two sample distributions of traffic volume on public roads were adjusted to sunset. The DVC rate was computed as the proportion of number of crashes to traffic volume.

The highest crash peak occurred 1 hour after sunset for both species of deer. The relative risk peaked at 30 times the seasonal daytime level of the crash rate for white-tailed deer in the fall and at over 60 times for moose in the summer.

Drivers can effectively reduce their risk of DVCs by reducing speed and remaining alert for deer intrusions on the roadway during the most critical time of the day: after sunset.