Bears, Elk and Even Mice Have Crossed Colorado's I-25 Wildlife Overpass

The Greenland Wildlife Overpass on Interstate 25 in Colorado now gets regular traffic of the four-legged kind. Elk, pronghorn, white-tailed deer, bobcats, bears and coyotes have all crossed it. So have skunks, weasels and mice, which is a lot of bridge for a mouse.¹⁰

“We are currently seeing multiple wildlife crossings per week on the Greenland Wildlife Overpass. Less than a year after construction was completed, a variety of wildlife has utilized the structure,” Maddie Garbalagtys, Denver Metro Communications Manager, Region 1 at the Colorado Department of Transportation (CDOT), told Hooray News in an email interview on Oct. 28, 2026.¹⁰

That matters for anyone who drives the stretch between Castle Rock and Monument. Before CDOT built its wildlife crossing system there, the corridor averaged about one wildlife-vehicle crash a day during the fall and spring migration seasons.⁵

The 91% drop came first

Our earlier story reported that wildlife crashes on this part of I-25 fell sharply before the overpass opened.¹¹ That result belongs to five large underpasses and roadside fencing installed in 2022 as part of CDOT’s South Gap project.⁴

A CDOT-commissioned monitoring study found wildlife-vehicle collisions dropped about 85% a year on average, reaching 91% in the study’s final year.³ Overall crashes fell about 20%, a figure likely shaped by roadway changes as well as the wildlife work.³ Garbalagtys confirmed the 91% figure to Hooray News.¹⁰

What the I-25 Greenland Wildlife Overpass adds

The Greenland Wildlife Overpass sits at mile point 165.4 near the Greenland interchange in Douglas County. It fills a 3.7-mile gap between crossings. It spans six lanes, measures 200 feet wide by 209 feet long, and links 39,000 acres of habitat to more than a million acres of Pike National Forest.¹ CDOT calls it North America’s largest wildlife overpass.⁵

CBS Colorado reported it opened in December 2025, ahead of schedule and under budget. It was funded with $22 million in federal money and $8 million from the state, and the contractor finished it for $15 million.⁴

Coverage of the study suggested the overpass may not reduce collisions much beyond what the underpasses already achieved.³ Garbalagtys explained why an open-air bridge still helps:

“For example, elk and pronghorn are more likely to use open crossings such as an overpass, which may help connect herds on the east and west sides of I-25. Over time, this connectivity could support greater genetic diversity within those populations.”¹⁰

Data on the overpass is still being collected. Researchers are gathering baseline genetic data on elk herds on both sides of the highway to compare in five to ten years.³

Gardening above six lanes of traffic

The overpass needed landscaping, too. “The overpass was covered with a native seed blend to match the surrounding environment. Vegetation management on the overpass is ongoing,” Garbalagtys said.¹⁰

CDOT recently hand-pulled weeds and scattered more native seed where plant cover was thin.¹⁰

A bighorn sheep overpass waits for funding

One planned crossing is on US 40 near Empire, at about mile point 257 near I-70 Exit 232, for the state’s largest herd of bighorn sheep.⁷ CDOT estimates it would cost $7 million to $10 million.⁷

The design has progressed through 90%, with a shelf set of plans issued in November 2023. CDOT has invested in finishing the design and the federal environmental review known as NEPA.¹⁰ “The project is currently on hold while CDOT continues to pursue additional construction funding,” Garbalagtys said.¹⁰

CDOT’s other priority areas include I-25 at Raton Pass, East Vail Pass, SH 160 near Mesa Verde, US 40 near Craig and US 287 near Fort Collins. A new state law is expected to raise roughly $3 million a year to match grants.⁴ The Colorado Wildlife and Transportation Alliance tracks these upcoming projects.²