Highways and Habitats: Wildlife-Vehicle Collisions Costs and Solutions

Reader Contribution by Mia Rishel and Faunalytics
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We’ve grown all too accustomed to the familiar scene: a dead animal on the side of the road, a sight that gets easier to ignore as days pass and the carcass no longer bears resemblance to a living creature. The sight is common, and the problem is one that receives little attention.

There is no recent estimate available, but in a 2008 report to Congress, the Federal Highway Administration estimated that in the U.S. alone, between one and two million collisions occur each year between cars and large animals. Each year, hundreds of Americans are killed in wildlife collisions and this number is only likely to rise: Collisions involving human fatalities increased by a staggering 67% from 1994 to 2006.

Biodiversity Toll of Vehicle-Wildlife Collisions

But while people more often than not come out of these interactions alive, animals are not as lucky. It is not easy to estimate how many animals die each year on U.S. roads as most collisions go unnoticed or unreported and most published studies concern large mammals only. The best estimate comes from the Humane Society, which has conducted several ambitious field studies across the country since the 1970s. Their estimate: one million vertebrates killed every day.

More so than any other nation, the landscape of modern America was shaped by cars. Every day, 200 million of them operate on millions of miles of road, paved and unpaved. And as we get into our cars, inattentively look out at our world from behind the windshield, and travel at speeds unnatural to any animal, it’s easy to feel disconnected to our environment — or even indifferent to it. It’s easy to think that because the roads we travel on were made by people and for people, we’re the only ones using them. The staggering number of animal deaths stated above tells us this isn’t the case.

In order to keep wildlife populations healthy, animals need room to roam as they engage in daily and seasonal activities like finding food, mates, shelter and rearing their young. Unfortunately, their spaces are broken up into smaller and smaller pieces by human infrastructure and development. This is known as habitat fragmentation and it’s one of the leading causes of habitat loss and subsequently the loss of species in the U.S. One key example of this impact is the Florida panther: Fewer than 250 individuals remain in the wild and as many as 20-30 are killed on roads each year.

Economic Costs of Wildlife Collisions

In addition to the devastating effects on our ecosystems and the tragic loss of human and animal life, there’s also the huge economic cost. Most people are completely unaware of the price tag of this issue, and it’s difficult to get an accurate cost estimate.

The most recent estimate available is from a decade ago. It put the annual cost of wildlife-vehicle collisions in the U.S. alone at over $8 billion. This number has likely increased since, for several reasons including a rise in the number of cars and miles traveled.

Solutions to Reduce Wildlife Road Deaths

Let’s compare this price tag to that of wildlife crossing construction. Sometimes all that’s needed is the clearing or altering of roadside vegetation to discourage animals from foraging next to the road and to give drivers better visibility of approaching animals. This is a low-cost solution.

In many places, an underpass, animal detection system or other cheap implementation can have a significant effect on collisions, and big, fancy overpasses actually make up a small percentage of crossings constructed. But let’s say an overpass is projected to have the biggest impact in a certain location.

Building and landscaping a large wildlife bridge can cost millions of dollars, but designed well and put in the right place, the benefit will eventually outweigh the cost. In addition, implementing the structure during the planning phase of infrastructure only marginally increases the cost, by an estimated 2 percent.

Wildlife crossings cost an average of $300,000 to $1 million to construct. With the total annual cost of wildlife-vehicle collisions, we could construct anywhere from 800 to 2500 crossings each year. Why don’t we?

Well, up until now there’s been some debate about whether they’re actually effective. And while there are some crossings that aren’t, we now have data that shows us that most of them are. They reduce collisions significantly and help people and animals get where they need to go safely. A handful of examples include the famous network of over- and underpasses in Banff National Park, which has reduced the number of wildlife collisions by over 80 percent.

In Colorado, a half dozen crossings reduced collisions on Highway 9 by 90 percent. In addition, genetic testing showed they’ve helped keep grizzly and black bear populations healthy by avoiding inbreeding. In Wyoming, a few over- and underpasses constructed where pronghorn and mule deer migratory paths crossed US 191 have reduced collisions by at least 90 percent.       

Scientists have produced enough evidence of the benefit of these crossings. Now we need voters, policy makers and stakeholders to acknowledge the problem and the need for change. If wildlife crossings became a standard consideration during road development, there would be a small impact for taxpayers, but a huge impact for everyone.

A million vertebrate animals killed by cars each day, costing $8 billion dollars per year. Two almost unfathomable numbers, directly related to each other. One could provide a solution for the other. Let’s start making efforts to balance the travel needs of people and animals and use the billions of dollars spent to prevent the millions of lives lost.


Chung, E. (2014, February 18). Banff bears use Trans-Canada wildlife crossings to find mates; wildlife crossings can cost up to $4m each, but benefit bear populations. News article retrieved from here.

Defenders of Wildlife. Reducing panther deaths on roads.

Hoffman, S. (2018, February 3). Animals are using Colorado’s wildlife crossings, reducing collisions, CDOT says. The Denver Post.

Mccollister, M. F., & Manen, F. T. (2010). Effectiveness of Wildlife Underpasses and Fencing to Reduce Wildlife–Vehicle Collisions. Journal of Wildlife Management,74(8), 1722-1731. doi:10.2193/2009-535

National Highway Transportation Safety Administration (2008). Fatality analysis reporting system.

Weir, E., (2002). Collisions with wildlife: the rising toll. Canadian Medical Association Journal, 166(6): 775.

Mia Rishel lives in Sweden where she is building an eco-friendly tiny house on wheels with her husband while working remotely on her Master’s in Zoology. She’s passionate about sustainable living and parenting and loves wildlife and farm animals. Previous work includes wildlife rehabilitation in the Pacific Northwest, fieldwork with endangered iguanas in Mexico, and farm animal welfare outreach in Tanzania. In her free time, Mia volunteers withFaunalytics, an animal welfare advocacy group.

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