Nine months after North America's largest wildlife overpass opened over I-25 in southern Douglas County, the agencies behind it have a number: wildlife-vehicle collisions on that stretch are down 91%.
The figure comes from CDOT's monitoring of the crossing system — the 209-by-200-foot overpass near the Greenland exit between Larkspur and Monument, plus five underpasses and fencing that guides animals to the crossings — as reported by CBS Colorado on Sept. 18.
"Based on the video feed that we're collecting, huge success," CDOT environmental manager Chuck Attardo told CBS. "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."
The before picture
For decades, I-25 was a wall across the seasonal migration routes that run through Douglas and El Paso counties. "This area was getting about one deer hit a day during those high movement periods in the spring and fall," Colorado Parks and Wildlife biologist Brandon Marette told CBS.
When CDOT completed the structure in December 2025, its own release framed the goal as a projection: the crossing system was "expected to reduce wildlife-vehicle crashes by 90%." Nine months of monitoring later, the measured number came in a point better.
What's using it
Per CBS's reporting, the first nine months of video show elk herds, pronghorn, bears, deer, and coyotes using the crossing. Biologists even piled wood into a pathway across the overpass for small mammals — cover, so coyotes, foxes, and hawks don't pick them off mid-crossing.
The pronghorn are the headline for wildlife watchers: CDOT says they're reaching the west side of I-25 for the first time in decades.
The build
The overpass spans all six lanes of the interstate and connects 39,000 acres of habitat on both sides, closing a 3.7-mile gap between other crossings, per CDOT's completion announcement. It was the final piece of the wildlife crossing system built alongside the I-25 South Gap project, which rebuilt 18 miles of the interstate from Castle Rock to Monument.
The project received $22 million in federal infrastructure funds and $8 million from the state — and Attardo told CBS that contractor Kraemer North America completed the build for about $15 million, ahead of schedule. By his math, crossings like this pay for themselves in about 15 years of avoided crashes.
One thing that hasn't gone to plan: the vegetation on the overpass deck struggled to germinate this year, per CBS. Crews plan to bring in new topsoil and reseed next year.
Driving that stretch this fall? The overpass sits in one of the prettiest runs of the county — the same Larkspur–Monument corridor covered in our fall colors guide.
Sources: CBS Colorado, Sept. 18, 2026 · CDOT completion release, Dec. 22, 2025. Photo: CDOT.