As wildlife-vehicle collisions on I-90 in western Montana pile up, the Montana Department of Transportation is launching a feasibility study for construction of a wildlife undercrossing – one that could also restore the natural flow of a creek to aid fish crossing.

[Above photo by HDR Engineering]

The study area is a 7.3-mile segment of I-90, centered on Sixmile Creek in Missoula County. Home to grizzly bears, black bears, elk, and deer, it is a “key linkage area” for wildlife between the Ninemile Valley and Bitterroot Range, according to Ben Schendel, project manager for Montana DOT.

Less than a mile south of I-90, Sixmile Creek connects to the larger Clark Fork River, which attracts wildlife from the forest and helps form a “movement corridor for multiple species of wildlife between large tracts of protected public lands to the north and south,” Schendel said. “Opportunities for wildlife to safely cross I-90 in this area are currently limited.”

More than a third of reported crashes in the corridor involve wildlife, nearly triple the statewide ratio, according to Montana DOT data. Multiple news sources reported in July that 11 elk trying to cross I-90 in the corridor were killed in one collision with a tractor-trailer. Additionally, a recent State Farm study showed that drivers in Montana were the second-most likely in the country to be involved in a wildlife-vehicle collision, with the odds placed at 1-in-53. (West Virginia ranked first at 1-in-40, the study found.)

Wildlife-vehicle collisions can be deadly for animals and motor vehicle occupants. According to a 2021 report by the Pew Research Center, as many as 2 million such collisions occur every year in the

U.S., killing about 200 people, injuring about 26,000, and causing at least $8 billion in damages and costs.

The proposed project would replace a 60-year-old culvert under I-90 with two vehicular bridges, eastbound and westbound, that would leave enough room below for a rehabilitated Sixmile Creek and a wildlife undercrossing. The pipe culvert under I-90 chokes down Sixmile Creek, altering its natural characteristics, leaving no room for wildlife to cross, and hindered the ability of trout to spawn.

Nearly 14 miles of eight-foot wildlife fencing along the interstate would steer wildlife to the undercrossing. Double cattle guards, electric mats and earthen jump outs near the fencing would discourage the wildlife from getting into the interstate right-of-way.

The Montana Fish, Wildlife, and Parks agency has “long recognized the Sixmile Creek culvert as an impediment to upstream passage for all fish species,” Schendel said. “The project would improve fish passage by removing the culvert and reconstruction the stream channel under the new bridges.”

Montana DOT held an in-person open house in October about the project and has a virtual open house on its project website. The site will take public comments through November 12.

While the agency currently does not have funds to build this crossing, it has scheduled activities in anticipation of a future funding decision, including stream design, preliminary bridge layout, and developing construction cost estimates.

A final report on the study is scheduled for August 2026, Montana DOT noted.

The Arizona Department of Transportation recently highlighted how one of the first steps in a project to widen US 93 near the town of Wikieup involved removing thousands of ocotillos, cactus, and other plants in the path of a newly divided highway.

[Above photo by the Arizona DOT]

The agency explained those native desert plants – more than 3,000 in all – weren’t obstacles to be discarded. Rather, their removal is only temporary as they’ve been carefully set aside to rejoin the desert landscape to help the landscape heal more quickly while minimizing the impact of this four-mile-long roadway construction project on the local environment.

“The goal is sustainability, visual integrity, and to continue the habitat for both wildlife and insects,” noted LeRoy Brady, Arizona DOT’s chief landscape architect, in a statement.

[Editor’s note: Salvaging native plants has been an important part of many Arizona DOT projects since the 1980s, including projects to widen Loop 101 in Scottsdale, the Loop 202 South Mountain Freeway and other improvement projects along US 93 between Wickenburg and Kingman.]

The US 93 project is saving ocotillos and about 15 species of cacti, the agency said – including barrel cactus, hedgehog cactus, Christmas cholla and staghorn cholla. They were removed when construction work began in early 2025 and have been cared for at a temporary nursery in the project area.

An irrigation system has kept the plants watered until their return along the new roadway, Arizona DOT said, with some plantings set to take place in early 2026 and the rest when the project nears completion in early 2027.

[Editor’s note: Across the country, state departments of transportation are involved in similar environmental activities, from maintaining flower beds for pollinators to planting trees in remembrance of fallen highway workers.]

The salvage efforts began with a survey of the plants to determine which species and individual plants were good candidates for saving based on decades of Arizona DOT’s experience with other plant relocation projects.

For example, that means knowing medium-sized ocotillos have high survival rates and are worth carefully digging up to store in the nursery.

“When you build a road, you want to keep as many of the plants as you can,” explained Robert Winrow, the Arizona DOT resident engineer who oversees the US 93 widening project. “The ultimate intent is to make it look like the road was always there.”

The plant restoration process will also include using a diverse mix of 25 to 30 native seed types where the ground was disturbed – with those seeds “customized” to that biological zone’s temperature, rainfall, and soil type, the agency said.

Those seeds range from grasses to perennials that will help control erosion, support pollinators, and just plain look good to motorists passing through. The diversified native re-vegetation through seeding will help prevent non-native invasive plant species from infesting the project area. 

While some of the native plants that will sprout from seeds and the transplants, such as hedgehog cactus, won’t be visible to motorists passing by at 65 mph, they’re just as important as the largest of the ocotillos that will rejoin the landscape as a diversity of plants is important to insects, birds, and other wildlife.

“Some things are hard to place a monetary value on but you do it because it all fits together,” Arizona DOT’s Brady said. “It’s a piece of the puzzle.”