Collaboration in Civic Spheres

UW study probes factors in Washington animal-vehicle collisions

by August 31st, 2011

SUMMARY: Collisions between vehicles and animals exact a large toll in injury and property damage every year in the U.S. and also have a significant impact in Washington state. A new study led by the director of a transportation research laboratory at the University of Washington in Seattle shows the probability of animal-vehicle collisions is increased on rural two-lane roads near white-tailed deer habitats, while the likelihood of such accidents is lowered if the road is wider, the animal is male rather than female, and the vehicle is a truck, not a car.

BACKGROUND: There are an estimated 1.5 million annual deer-vehicle collisions in the U.S. and in Washington State, about 3,000 a year between vehicles and deer or elk on Washington state highways alone. Animal-vehicle collisions cause about 200 human fatalities and 20,000 human injuries per year in the U.S. and result in annual property damage exceeding $1 billion. A new statistical model was devised by a University of Washington research team to improve understanding of the human, animal and interactive factors contributing most greatly to such mishaps. In their study researchers used animal carcass removal data from the Washington State Department of Transportation including location, date, weather, animal type, sex and age; GIS-based maps showing population distribution in the state for mule-deer, white-tailed deer and elks; and official data on road and shoulder width, and speed limits.

KEY LINK: “Modeling Animal Vehicle Collisions Considering Animal-Vehicle Interactions,” draft of paper to be published in November, 2011 edition of  Accident Analysis and Prevention. Lead author: Yinhai Wang, Department of Civil and Environmental Engineering; Director, Smart Transportation Applications and Research Laboratory; University of Washington.


  • Higher speed limits and higher driving speeds increase the probability of an animal vehicle collision. Vehicles traveling at higher speeds need a longer stopping distance if an animal is spotted in the road, and the reaction time is less. The driver’s probability of an ineffective response “goes up significantly” when the speed limit on the road is greater than 50 mph.
  • Rural, two-lane roads and the presence of a white-tailed deer habitat also increase the likelihood of collisions between vehicles and animals. There are more animals in rural areas, and data show that driving through white-tailed deer habitat makes the probability of a collision “much higher.” Transportation agencies should consider lowering speed limits on roads which go through or adjacent to white-tailed deer habitats.
  • Animal-vehicle collisions are less likely to occur if the animal is male, the vehicle is a truck, and the road has a relatively large number of lanes. Male animals have a lower risk of collision because they’re more alert; they respond to collision threat and run away faster than females. Trucks typically go slower than passenger vehicles and the driver’s seating is elevated, improving sight lines. In addition, trucks are noisier, improving warning signs to animals in or near the road.

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3 Responses to “UW study probes factors in Washington animal-vehicle collisions”

  1. K says:

    As an alumni of the CEE Department at UW, let me be the first to say – this study is an Embarrassment. Why in the world are we spending money modeling something that any average person who drives in the countryside knows.

    Also, I find the statistic “1.5 million annual deer-vehicle collisions in the US” extremely suspect, as Washington (3,000 collisions per year) then has only ~0.2% of the collisions. Where are all these other collisions happening at such a higher rate?? Is the Midwest or the Eastern Seaboard just littering the roads with deer and elk?

    All in all, thus study is a waste of time and energy, and should be a lesson for the future that not everything needs to be modeled.

  2. Thanks for your comments, K. The rough estimate cited in the study of about 3,000 annual collisions by vehicles with deer or elk in Washington state refers to collisions on official state highways only. There could be more which occur on county-maintained or local roads.

    As far as whether the findings of the study are useful or not, it’s a matter of perspective. I think the specificity regarding greatly increased risk around white-tailed deer habitat is a very useful point of information. And while the issue of speed seems obvious, lowering of speed limits below 50 on rural state highways near white-tailed deer habitats is a very specific and – if the modeling is to be believed – potentially helpful prescription. One that has not been implemented yet, almost certainly because the necessary research had not convincingly shown the need.

    Lastly, and for what it’s worth, I would humbly suggest that -while we DO allow anonymous comments here – that when a commenter is saying something on the order of, “As an alumni of the CEE Department at UW, let me be the first to say – this study is an Embarrassment,” that whatever your other arguments, it enhances your credibility a lot if you have the gumption to stand behind your full name.

    Just as the authors of the study did.

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