Colorado Is Building the ‘World’s Largest’ Wildlife Overpass, Giving Elk and Other Big Creatures a Safe Path to Cross a Busy Freeway

The completed overpass will be 200 feet wide by 209 feet long, forming a bridge across six lanes of traffic that see more than 100,000 vehicles each day

Sarah Kuta | Daily Correspondent

August 4, 2025

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Twice a year, thousands of elk, mule deer and pronghorn migrate between their seasonal ranges in Colorado. They spend their winters grazing at lower elevations and their summers in the mountains.

As they make these semiannual journeys, however, the ungulates must often traverse busy, high-speed roadways—and these crossings can have disastrous consequences for both the animals and human motorists.

Now, Colorado is building a massive new bridge to help make one bustling freeway safer for all species. Construction is underway for a $15 million overpass that, once it’s finished as soon as December, is expected to be the largest wildlife crossing in the world, according to a statement from the Colorado Department of Transportation.

Crews are building the bridge over Interstate 25, a highly trafficked, north-south thoroughfare connecting many of Colorado’s major cities. It’s being constructed north of the town of Monument, roughly 50 miles south of Denver, in a 3.7-mile gap between existing wildlife crossings.

The project is a partnership between the Colorado Department of Transportation, the Federal Highway Administration, Colorado Parks and Wildlife, Douglas County and other partners. According to the Colorado Department of Transportation, most of the funding comes from the U.S. Department of Transportation via the 2021 Bipartisan Infrastructure Law, which is supporting the construction of dozens of wildlife crossings across the country through a series of grants.

The bridge is the final component of a broader wildlife crossing system that consists of underpasses and fencing. The infrastructure is located along an 18-mile stretch of the highway between Colorado’s biggest cities, Denver and Colorado Springs, and sees more than 100,000 vehicles each day. Before crews started the project, the corridor saw an average of one wildlife-vehicle crash per day during the spring and fall migration periods.

“There are always kind of serious crashes there,” says Kara Van Hoose, a spokeswoman for Colorado Parks and Wildlife, to Cowboy State Daily’s Mark Heinz.

Once the overpass is finished, however, officials expect animal-car crashes to drop by 90 percent, according to the statement.

Smaller animals are already using the I-25 underpasses. But officials hope the new overpass will be more appealing to bigger game animals like elk, which prefer clear sight lines and space to accommodate their large antlers. “Elk love big open structures,” says Chuck Attardo, the I-25 south corridor environmental manager for the Colorado Department of Transportation, to the Colorado Springs Gazette’s Savannah Eller.

They expect moose, black bears, mountain lions and other creatures to use the bridge, too. The animals should have plenty of room to spread out as they amble across the overpass, which spans six lanes of traffic. The completed structure will be 200 feet wide by 209 feet long, covering an area that measures 41,800 square feet, or nearly an acre. It’s strategically located in an area where large game creatures are already known to be active and will link 39,000 acres of habitat protected by the Douglas County Land Conservancy with more than one million acres of Pike National Forest.

The entrances are wide and gradually sloped, which designers hope will make the bridge inviting to large animals.

“This was a place where we were seeing a pretty high incidence of collisions,” says Shoshana Lew, executive director of the Colorado Department of Transportation, to KKTV’s Elmer Sagastume. “The wildlife using it are bigger, so part of the reason we need a more comprehensive structure is to make sure they’ll actually use it.”

Wildlife-vehicle crashes are a major problem throughout Colorado. So far this year, Colorado State Patrol has recorded 1,600 vehicle crashes involving wildlife across the state, report KMGH-TV’s Landon Haaf and Claire Lavezzorio.

“Everybody thinks it’s just in rural areas. No, it’s everywhere in Colorado,” says Sherri Mendez, a spokeswoman for the agency, to KMGH-TV. “And we’re here to warn people to be more cognizant of the roadways, because wildlife will come into the metro area.”

To address this issue, the state has been on a building spree. It has constructed 28 new large game crossing structures since 2015, as Catrin Einhorn reported for the New York Times in March.

Colorado is not the only state trying to use infrastructure to reduce animal-car collisions. In California, crews are putting the finishing touches on the new Wallis Annenberg Wildlife Crossing, a $92 million overpass over Highway 101 in Los Angeles County. That bridge will measure 210 feet by roughly 174 feet, which makes it slightly smaller in area than the Colorado overpass.

Sarah Kuta | Read More

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.