Bridging the Divide: How to decrease wildlife-vehicle collisions

Now is the time to implement wildlife accommodation measures on our local highways. That’s the key takeaway from the U.S.-191/MT-64 Wildlife and Transportation Assessment recently published by the Center for Large Landscape Conservation and Montana State University’s Western Transportation Institute.

According to a 2022 National Park Service report cited in the assessment, more than 1 million vehicles use 191 to enter Yellowstone from the west, and a quarter of all crashes in their study area involved wildlife. Between 2011 and 2020, the transportation department and the Interagency Grizzly Bear Study Team documented 1,322 animal carcasses along U.S. 191 and MT 64, and the true number of road-killed could be eight times higher, researchers claim.

“These roads are really kind of the only public access to the community of Big Sky and one of the main routes between Bozeman and West Yellowstone, and these roads are getting a lot busier,” said CLLC road ecologist and report lead author Elizabeth Fairbank at an October 23 public forum in Big Sky. “We saw a 38 percent increase in traffic volume along 191 from 2010 to 2018, and that’s just continuing to go up now. More traffic is a problem for wildlife, both in terms of increased wildlife-vehicle collisions, as well as the road becoming more and more of a barrier to wildlife movement.”

While the entire study area from Bozeman to West Yellowstone and MT 64 through Big Sky is quality wildlife habitat, the assessment identified 11 priority sites to focus on, each with unique considerations and different solution recommendations.

For example, a 5.6-mile stretch of 191 between Gallatin Gateway and Spanish Creek has a high wildlife-vehicle collision potential due to migrating ungulates, particularly deer and elk. “We have lots of species that need to move here in the Greater Yellowstone Ecosystem,” Fairbank said. “Many of these herds’ migration corridors cross through our study area and these animals need to be able to move long distances between winter and summer ranges, and have to cross through a matrix of public land, private land, roads and fences to get to where they need to go.”

Between Gateway and Spanish Creek in the Gallatin Canyon, specially designed pathways added beneath the existing bridge that leads over the Gallatin River could accommodate large mammals, even at high water. Additional fencing along the road would direct animals safely toward the underpass. “Thankfully, there are a variety of different measures aimed at reducing wildlife-vehicle collisions and maintaining habitat connectivity,” Fairbank added.

Just north of the MT 64 junction, bighorn sheep often feed adjacent to the road, and elk migrate across the highway from the Gallatin Range in the east to the Lee Metcalf Wilderness to the west. To minimize collisions, CLLC identified a similar bridge retrofit with an accessible underpass, but also called for an overpass that could better serve the same purpose. As the assessment notes, what solutions are chosen will ultimately come down to a variety of factors, including cost, land ownership and public support.

Beyond the impact to wildlife, there is a financial incentive to protect animals along these stretches of road. According to the study, average direct costs—vehicle repair, human injuries and fatalities—for a collision involving deer come in at more than $14,000; for elk the cost is over $45,000, and for moose collisions it’s nearly $83,000.

“Between 2011 and 2020, Department of Transportation and Interagency Grizzly Bear Study Team documented over 1,300 large wildlife carcasses within our study area,” Fairbank said. “A conservative cost estimate for that is $27 million, just in the direct costs. If you add in the intrinsic value of wildlife, that goes up to $60 million just in 10 years.” In 2021, 4.9 million visitors to Yellowstone National Park created an $834 million cumulative economic benefit to local communities adjacent to the park, according to the National Park Service.

While decreasing road traffic might seem like an obvious part of the solution, researchers say it’s not so simple. “Changing driver behavior... we still text and drive, we still drink and drive. So, to say ‘Oh flashing lights, everyone’s gonna slow down and increase their awareness to avoid wildlife collisions,’ that’s not nearly as effective as having the structures,” Rob Ament from the Western Transportation Institute said during the October 23 public forum. “Traffic levels are high enough where not only is it a safety issue of collisions, it really is becoming a barrier effect and that’s what is poorly understood.”

Ament cited a Glacier National Park study led by wildlife biologist John S. Waller on Hwy. 2 along the south border of Glacier to illustrate his point. “The researchers had collared grizzly bears and they put traffic counters out, and they found that the bears only crossed when there were 100 vehicles per hour or less. So that would be 2,400 vehicles a day, and you saw the numbers—10,000 and higher on some sections of Hwy. 191. I can almost assure you it’s already, for some sensitive species, either a partial or total barrier for their movement.” As Ament stated, human driving behavior is unlikely to change, so reducing traffic flows by 75 percent could prove far more difficult than installing crossing structures, and far less effective. “Structures with fencing [reduce collisions] 80 to 100 percent,” he said.

With the problem clearly identified and real-world solutions already in use elsewhere, there are reasons to be hopeful, according to Fairbank, the CLLC road ecologist. “On Hwy. 191 in Wyoming at Trappers Point just outside of Pinedale … they installed two overpasses and six underpasses with fencing,” she said, “and they saw an increase of 600 percent in back-and-forth movement by pronghorn. So there has been good evidence that once you build [the structures] their ability to access and their ability to cross back and forth is rising.”

While road infrastructure projects are notoriously slow-moving, wildlife accommodations could benefit from broad public support, traction with local and state governments and funding opportunities at the federal level. “This assessment is kind of step one,” Fairbank said. “A big thing that we’re going to be working on over the next few months is to have our results get integrated into the [Context Sensitive Solutions] optimization plan that MDT is working on so that we can make sure that as they’re planning out projects over the next decade that all this stuff is incorporated.”

As study results move toward on-the-ground realities, funding will be key. “All of these projects are big and expensive,” Fairbank continued. “There’s a bunch of different pots of federal infrastructure money that could be used for these projects, so we’re just trying to connect the dots and figure out which pots of money are the best fit for some of the different projects we’ve identified.”

In the meantime, researchers are encouraging the public to review the report, provide feedback, and contribute data through on-the-ground citizen science. NPS and the U.S. Fish and Wildlife Service partnered with the Western Transportation Institute to develop a smartphone app called ROaDS, which allows observers to report wildlife sightings, crossing attempts and road-killed carcasses. Download it by emailing Braden Hance at bradenhance@largelandscapes.org.

At the state level, MDT has undertaken their own study of the U.S. 191 corridor between Four Corners and Beaver Creek, which CLLC’s assessment will inform. Their report is also open for public feedback at mdt.mt.gov/pubinvolve/us191.