Colorado's Giant Wildlife Overpass Completes a System That Cut Animal Collisions 91%

A stretch of Interstate 25 south of Denver has become markedly safer for both drivers and animals. A Colorado Department of Transportation (CDOT) study found wildlife-vehicle collisions on the South Gap corridor dropped 91 percent in the last year it covered, Colorado Politics reported on 28 September 2026.

The numbers

• The study covered 2022 to 2024 and found an average annual reduction of about 85 percent.
• Before the work, wildlife were involved in an average of 32 crashes a year, the third most common crash type on that section.
• Overall crashes on the section fell 20 percent, which CDOT attributes to roadway changes as well as wildlife measures.

What was built

The system includes five underpasses and 14 miles of fencing on each side of the highway. Its final piece, the Greenland Wildlife Overpass, was completed in December 2025. At 200 by 200 feet and $15 million, CDOT calls it the largest of its kind in North America. It was funded through the Federal Highway Administration's Wildlife Crossings Pilot Program.

Early signs on the overpass

Elk and pronghorn are more likely to use open crossings like overpasses, a CDOT spokesperson said, which could reconnect herds that the highway once split. Cameras have recorded elk, pronghorn and bears on the bridge. Julia Kintsch, principal investigator on the overpass study, called the early footage "a really promising sign."

Context

The 91 percent figure reflects the whole mitigation system, not the overpass alone, and the overpass is still new. Initial results on how well it works are expected in spring 2027.