Largest wildlife overpass has cut wildlife-vehicle collisions by 91%, report finds
Pronghorn have used the overpass to cross Interstate 25 safely for the first time in 30 years, while bears, coyotes, deer, elk, moose, frogs, and a threatened species of mouse have also been taking advantage of the $15 million crossing.
The I-25 Greenland Wildlife Overpass near Larkspur, which is North America’s largest wildlife overpass. Credit: Colorado Parks and Wildlife
Ten months after it was completed, the largest wildlife overpass in North America has been hailed a “big success”, credited with reducing wildlife-vehicle collisions by 91%, according to a newly released report.
The 209-by-200-foot overpass – which spans six lanes of traffic on Interstate 25, near the Greenland exit between Larkspur and Monument in Douglas County, Colorado – has been used by big game, reptiles, rodents, and amphibians.
Until now, accidents and delays were a common sight on this stretch of highway that links the state’s two most populous cities, Denver and Colorado Springs, with more than 100,000 motorists using it each day. Big game animals like deer, elk, and pronghorn fared particularly badly when trying to cross and, during seasonal migrations between fall and spring, an average of one wildlife fatality occurred every day.
However, thanks to the new overpass, just two such accidents have been reported, said the Colorado Sun. This, in turn, has also led to a 9% reduction in travel delays.
The Colorado Department of Transportation (CDOT) had already erected 14 miles of eight-foot-tall fences on both sides of the freeway, and built five wildlife underpasses. The overpass – which was finished by the contractor Kraemer North America ahead of schedule and $7 million under budget – fills a 3.7 mile gap between the other crossings, and was designed specially for big game animals who favour wide, open spaces over enclosed underpasses and tunnels.
“Elk and pronghorn like these big open structures where they can see for miles in each direction,” Chuck Attardo, CDOT environmental manager, told CBS News. “For decades, pronghorn going from Trinidad to Greenland were looking for a place to cross on I-25. And when we open this up, we have pronghorn on video using the overpass, and for the first time in decades they’re coming over here to the west side.”
In June, it was confirmed that a pronghorn had safely crossed I-25 for the first time in 30 years. Herds of elk have also taken advantage of the crossing, and Brandon Marette, a wildlife biologist for Colorado Parks and Wildlife, described seeing footage of an elk crossing I-25 with her calf as “a heartwarming moment.” “All the hard work for six years all came to fruition in that one moment,” he told CBS News. “That elk with her calf was just standing there in safety, getting to the other side of I-25.”
In a further boost, cameras have revealed that an array of animals are using the overpass, including wolves, bears, moose, coyotes, rabbits, northern leopard frogs, and even the Preble’s meadow jumping mouse, a threatened species found only in Colorado and Wyoming.
Coyotes running near the Interstate 25 overpass in August 2026. Credit: Colorado Department of Transportation
Attardo justified the $15 million cost of building the overpass, saying that it will soon pay for itself, due to all the accidents prevented. According to the U.S. Department of Transportation’s Federal Highway Administration, there are over one million wildlife-vehicle collisions every year, leading to around 59,000 injuries and $8 billion in damage. Approximately 400 human lives are lost in these collisions, with countless more animal deaths.
As such, Attardo said that CDOT is looking to build more crossings, including the first wildlife overpass specifically designed for Rocky Mountain bighorn sheep along Colorado 40, east of Empire.
And starting in January, the Colorado Sun reports that motorists will have the chance to opt in to a $5 fee that goes towards funding the construction of wildlife passes across the state.
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Pronghorn have used the overpass to cross Interstate 25 safely for the first time in 30 years, while bears, coyotes, deer, elk, moose, frogs, and a threatened species of mouse have also been taking advantage of the $15 million crossing.