Colorado Opens Largest Wildlife Overpass in North America Along I-25

DOUGLAS COUNTY, CO – A new landmark piece of infrastructure is now complete along Interstate 25 south of Denver, where the Colorado Department of Transportation has finished construction of what is currently the largest wildlife overpass in North America.

Photo from Denargo Market Block 6 Urban Design Application

The structure spans all six lanes of I-25 near Larkspur and reconnects tens of thousands of acres of habitat that were long divided by the highway. Built to support wildlife movement rather than vehicle traffic, the overpass is designed to blend into the surrounding landscape, with soil and native vegetation placed on top to resemble natural terrain.

This section of I-25 sits within a major wildlife migration corridor and has historically been one of the more dangerous stretches of roadway for animal crossings. Large species such as elk, pronghorn, mule deer, black bears, and mountain lions frequently move through the area, often during seasonal migration periods when vehicle-wildlife collisions were common.

The newly completed overpass addresses a gap between existing wildlife underpasses installed as part of the I-25 South Gap improvements between Castle Rock and Monument. While underpasses have proven effective for many species, the Greenland crossing was intentionally designed as a wide, open structure to better accommodate animals that are less likely to enter enclosed spaces, particularly elk and pronghorn.

At more than 200 feet wide and covering nearly an acre, the overpass functions as a continuation of the surrounding landscape rather than a traditional bridge. Fencing along the highway directs animals toward the crossing, reducing the likelihood that wildlife will attempt to cross the interstate at grade.

Beyond ecological benefits, the project is expected to significantly improve roadway safety. Prior to the construction of wildlife crossings in this corridor, the area experienced frequent wildlife-vehicle crashes, especially during spring and fall movement seasons. Transportation officials estimate that the completed system of crossings and fencing could reduce those incidents by as much as 90 percent.

The project was delivered through a coordinated effort involving CDOT, Colorado Parks and Wildlife, Douglas County, federal transportation agencies, and local land conservation organizations. Funding was largely supported through a federal wildlife crossings grant program, reflecting a broader shift toward integrating wildlife considerations into major transportation projects.

With construction now complete, monitoring will begin to track how wildlife use the structure over time. The overpass represents a growing approach in Colorado infrastructure planning, where transportation improvements are designed not only to move people efficiently, but also to maintain ecological connectivity across the state’s busiest corridors.

All project information was sourced from publicly available site plans, renderings, and permitting documents.

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All project information was sourced from publicly available site plans, renderings, and permitting documents.