About the research
More than 7,300 crashes involving animals, mainly white-tailed deer, are reported in Iowa each year, accounting for 13.5% of all reported motor vehicle crashes. Previous research indicates that law enforcement reports undercount the actual number of deer crashes, but the extent of this underreporting in Iowa was unknown.
To assess the prevalence of unreported deer crashes, this project conducted public surveys of two samples, one recruited through a market research firm and the other recruited through the Iowa Department of Transportation’s (DOT’s) social media presence. The results indicate that about 40% of deer crashes are not reported to law enforcement and, contrary to the requirements of state law, the severity of the property damage sustained in a crash only weakly affects whether it is reported. The results also suggest that carcass counts substantially undercount deer crashes, with respondents indicating that about 40% of deer run away after the crash, while 20% end up on the road shoulder, and another 17% end up in the ditch, weeds, woods, etc. Respondents also indicated that around 60% of the deer-vehicle crashes in which they were involved occurred on paved two-lane rural highways or unpaved rural roads, about 20% occurred on freeways, and around 20% occurred on urban, suburban, or small-town streets.
Mapping of Iowa vehicle-animal crashes that were reported to law enforcement in 2010–2020 indicates that although crashes occur throughout the state, they are most prevalent in southeast and northeast Iowa, on routes that parallel rivers and other waterways, near river crossings, and in the southwestern suburbs of the Des Moines metropolitan area. Animal crashes are less prevalent in northwest and north-central Iowa, except near river crossings. Combinations of high traffic volume and high-quality deer habitat appear to increase the likelihood of motor vehicle crashes involving animals. Fatal vehicle-animal collisions in Iowa often involve motorcycles or loss of control.
In addition, this project considered likely deer-vehicle seasons and times of day, reviewed previous research on the potential effectiveness of various countermeasures, assessed methods for automating the collection of deer crash location information, and estimated a recommended value for the comprehensive costs of a typical deer crash.