Deer–Vehicle Crashes Extensive Peak at 1 Hour After Sunset Hannu Haikonen, BA, Heikki Summala, PhD Background: 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. Methods: 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. Results: 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. Conclusions: 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. Medical Subject Headings (MeSH): accident prevention; circadian rhythm; accidents, traffic; behavior, animal (Am J Prev Med 2001;21(3):209 –213) © 2001 American Journal of Preventive Medicine O n-road encounters with animals, particularly deer, resulted in the deaths of 231 people involved in 213 crashes in the United States during 1999. 1 National deer roadkill for 1991 was estimated to total at least 500,000 animals. 2,3 In Europe, excluding Russia, the number of collisions with ungu- lates (hoofed animals) has been estimated at half a million, resulting in 300 people killed and 30,000 injured annually. 4 Evidently, in addition to the human and economic losses caused by these crashes, the damage to the wildlife population is also an issue of serious concern. 5 The percentage of deer–vehicle crashes (DVCs) that lead to human injuries largely depends on the deer species in the particular region. In Finland, our study area, 9.9% of the recorded crashes with moose and 1.3% of the recorded crashes with white-tailed deer resulted in injuries or fatalities during 1989 to 1997. A collision with a moose may result in the body of the animal partially penetrating into the automobile through the windshield and in the violent bending of the roof just above the heads of the front passengers. 6–9 Consequently, the most serious and fatal injuries typi- cally result from a heavy blow to the head, with the injury risk increasing with the deformation of the car. 6,7 With smaller species of deer, a greater proportion of fatalities result from secondary collisions due to avoid- ance maneuvers or loss of control. 10 During 1999, 69 of the 213 fatal crashes in the United States did not involve an actual collision with an animal, but resulted from unfortunate maneuvers in avoiding one. 1 In proportion to the extent of the problem, there has been little research undertaken in this field. 2,4,5 At the same time, various policies employed at reducing DVCs have been extensively used in many areas with little scientific evaluation of the expected or actual effect. 2 For instance, of the 43 states responding to a survey investigating the management actions taken to reduce deer–vehicle crashes, 40 used deer-crossing signs, 22 used public awareness programs, and 22 had installed swareflex reflectors. Seven of the 43 states had gone as far as building or modifying underpasses or overpasses for deer, seven had set lower speed limits, and six had altered the animals’ habitat. 2 From the Traffic Research Unit, Department of Psychology, Univer- sity of Helsinki, Helsinki, Finland Address correspondence and reprint requests to: Heikki Summala, Traffic Research Unit, Department of Psychology, University of Helsinki, P.O. Box 13, 00014 Helsinki, Finland. E-mail: heikki. summala@helsinki.fi. 209 Am J Prev Med 2001;21(3) 0749-3797/01/$–see front matter © 2001 American Journal of Preventive Medicine • Published by Elsevier Science Inc. PII S0749-3797(01)00352-X