A new wildlife crossing system is making humans and animals safer in Colorado, officials say. Wildlife-vehicle collisions are down more than 90 percent along a busy stretch of freeway in the state, reports Colorado Politics’ Savannah Eller, thanks to new infrastructure that helps animals safely cross over and under the road. The reduction in crashes comes along 18 miles of Interstate 25, a north-south thoroughfare connecting many of Colorado’s major cities.
More than 100,000 vehicles travel this section of the interstate every day, cutting through some 39,000 acres of wildlife habitat. That proximity put elk, pronghorn, mule deer and numerous other species at risk whenever they wanted to cross from one side to the other. Human drivers faced the threat of dangerous—potentially deadly—collisions, too.
So, three decades ago, local, state and federal officials decided to address the problem head-on. In 1996, they began working on a series of strategically engineered wildlife crossing structures along the interstate between the towns of Castle Rock and Monument. They built 14 miles of eight-foot-tall fences on both sides of the freeway and installed five wildlife underpasses.
In December 2025, officials celebrated the completion of the project with the opening of a $15 million wildlife bridge near the town of Monument, roughly 50 miles south of Denver. The bridge, which officials say is the largest of its kind in North America, fills a 3.7-mile gap between the other crossings. The bridge measures 200 feet wide by 209 feet long, with a surface area of about 41,800 square feet—just shy of an acre.
The overpass is designed for large game animals, which tend to prefer wide-open spaces with clear sightlines—and, so far, it appears to be working as intended. Elk have been caught on camera ambling across. And for the first time in years, pronghorn are wandering over to the west side of I-25.
Surveys and trail cameras have revealed rabbits and northern leopard frogs using the overpass, per the Colorado Sun’s Olivia Prentzel. Officials have tried to make the overpass, which spans six lanes of traffic, appealing to small mammals like the threatened Preble’s meadow jumping mouse by piling logs into a pathway to provide cover from predators such as coyotes, foxes and hawks. They’re also hoping to get more vegetation to grow on the overpass next year, as this year’s drought affected germination.
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