Colorado's I-25 Greenland Wildlife Overpass Cuts Collisions 91 Percent Nine Months After Opening

DOUGLAS COUNTY, Colorado - Nine months after North America's largest wildlife overpass opened over Interstate 25 near Greenland, Colorado officials told CBS Colorado that a mitigation system of the overpass, five underpasses and fencing has cut wildlife-vehicle collisions along the corridor by 91 percent, with video showing elk herds and pronghorn using the crossing.

The 209-by-200-foot structure spans six lanes of interstate traffic between Larkspur and Monument in Douglas County. It was designed especially for elk and pronghorn, species that prefer wide-open sight lines and historically avoided the enclosed underpasses already built along the I-25 South Gap corridor from Castle Rock to Monument. Colorado Department of Transportation research and press materials describe the overpass as completing that system by closing a former 3.7-mile gap in safe passage.

Chuck Attardo, CDOT environmental manager for the corridor, told CBS Colorado the video evidence has been decisive. "Based on the video feed that we're collecting, huge success. We're seeing elk herds cross the bridge. We're seeing pronghorn for the first time in decades cross over to the west side of I-25 because of the bridge," he said. Attardo added that elk and pronghorn "like these big open structures where they can see for miles in each direction," and that pronghorn moving between Trinidad and Greenland had long lacked a safe place to cross until the overpass opened.

Before the broader system was in place, the stretch between Castle Rock and Monument averaged about one wildlife-vehicle crash a day during peak spring and fall movement seasons, according to CDOT and Colorado Parks and Wildlife. Brandon Marette, a CPW wildlife biologist, told CBS that I-25 had functioned as "an effective wall" animals had to try to cross. In the nine months since the overpass opened, officials said the structure has also carried bears, deer, coyotes and smaller animals; biologists piled wood into a pathway so coyotes, foxes and hawks would be less likely to pick off rodents and amphibians mid-crossing, including habitat used by the federally threatened Preble's meadow jumping mouse.

CDOT completed construction in December 2025, covering the deck with soil and vegetation, ahead of schedule and, according to CBS Colorado citing Attardo, under budget at about $15 million after federal infrastructure funds and state matching money were allocated. The agency's December 2025 announcement called the finished bridge the single largest wildlife bridge structure in North America, covering roughly 41,800 square feet, and said it reconnects about 39,000 acres of habitat managed with partners to more than a million acres of the Pike National Forest. Partners named by CDOT and CBS include the Federal Highway Administration, Colorado Parks and Wildlife, Douglas County, the Douglas Land Conservancy and the Colorado Cattlemen's Agricultural Land Trust. Contractor Kraemer North America built the span.

Attardo told CBS that wildlife crossings tend to pay for themselves in roughly 15 years through avoided crashes, property damage and delays, and that CDOT is identifying further priority corridors across the state as federal and new state matching funds become available. For Marette, one image captured the point of the work: an elk cow and calf standing safely beneath the interstate. "All the hard work for six years," he said, "all came to fruition in that one moment."

Sources

1. CBS Colorado: Largest wildlife overpass in North America located in Colorado with 91% reduction in collisions (18 Sep 2026)
2. CDOT: Completes construction of the I-25 Greenland wildlife overpass (22 Dec 2025)
3. CDOT project page: I-25 Greenland Wildlife Overpass
4. Axios Douglas County: A highway fix that could save Colorado's wildlife (27 Apr 2026)