Colorado opens North America’s largest wildlife crossing

The new overpass spans six highway lanes.

Colorado opened the I-25 Greenland Wildlife Overpass in December 2025, and it is now North America’s largest wildlife crossing by surface area.

The Colorado Department of Transportation announced the opening on December 22. The massive structure sits near Larkspur in Douglas County, between Castle Rock and Monument.

More than 100,000 vehicles travel this stretch of Interstate 25 every day, making it one of the busiest corridors in the state.

Structure covers nearly one acre

The overpass measures 200 feet wide and 209 feet long, covering nearly one acre of space. That adds up to 41,800 square feet of crossing area for wildlife.

The structure spans all six lanes of interstate traffic below. Engineers used 76 steel girders to support the massive weight.

Workers covered the surface with dirt and native plants to make it look and feel like natural terrain for animals walking across.

Elk and pronghorn need open crossings

Builders designed the overpass specifically for elk and pronghorn. These animals avoid tunnels and enclosed structures because they feel trapped inside them.

Their large antlers also make underpasses uncomfortable to navigate. Both species prefer wide open crossings where they can see in all directions.

Deer, bears, and mountain lions will also use the new crossing, but elk and pronghorn were the main reason engineers built an overpass instead of a tunnel.

Crashes happened daily during migrations

Before the crossing system existed, wildlife-vehicle crashes happened about once per day during migration seasons.

Most crashes occurred in fall and spring when animals move between their summer and winter ranges.

Colorado records nearly 4,000 wildlife-vehicle crashes every year across the state. These collisions cause injuries, deaths, and cost an estimated $80 million annually.

The corridor sits in a major migration zone between Denver and Colorado Springs.

Overpass connects 39000 protected acres

The new structure connects 39,000 acres of protected land on both sides of Interstate 25. It links Douglas County Land Conservancy property to more than one million acres of Pike National Forest.

This creates the largest stretch of connected habitat along Colorado’s Front Range. Animals expected to use the crossing include elk, mule deer, pronghorn, black bears, mountain lions, and moose.

Wildlife cameras now track every animal that walks across.

Crossing completes 18-mile network

The overpass completes an 18-mile wildlife crossing network along this section of highway. Crews built five wildlife underpasses as part of the I-25 South Gap project back in 2022.

Animals have already started using those tunnels regularly.

The new overpass fills a 3.7-mile gap that existed between those underpasses.

The full system also includes 28 miles of wildlife fencing that guides animals toward the safe crossings.

Underpasses cut crashes by 91 percent

Research from the Colorado Department of Transportation shows the five underpasses work well for many species.

As of August 2025, the underpass system had reduced wildlife-vehicle collisions by 91 percent in that area.

Smaller animals like deer and bears use the tunnels comfortably. But elk and pronghorn kept avoiding them, which is why the overpass was necessary.

Together, the full crossing network should cut crashes by about 90 percent.

Project cost $15 million total

The construction cost came to $15 million. The Federal Wildlife Crossings Pilot Program provided most of the money.

In total, the project received $22 million in federal funds and $8 million from the state of Colorado. Kraemer North America finished the work under budget.

The leftover money will go toward extending wildlife fencing along the corridor to guide even more animals toward safe crossings.

Crews finished 10 months early

Construction began in January 2025, and crews finished the project in about 10 months.

The Colorado Department of Transportation had originally planned for completion by December 2025, so the early finish was a welcome surprise.

Kraemer North America also built the I-25 South Gap highway project a few years earlier. Because the contractor already knew the location and its challenges, the work moved faster than expected.

Nine years of planning were involved

The Federal Highway Administration helped fund and oversee the project from start to finish.

Colorado Parks and Wildlife provided expertise on animal behavior and migration patterns.

Douglas County handled local coordination with nearby communities. The Douglas Land Conservancy and Colorado Cattlemen’s Agricultural Land Trust also contributed to the effort.

Planning for the overpass took more than nine years before construction could begin.

Colorado plans six more crossings

Colorado has now built more than 100 wildlife crossing structures across the state. Only three of those are overpasses, which large animals strongly prefer over tunnels.

The Colorado Department of Transportation has identified six more priority locations for future crossings.

These include Raton Pass, U.S. 287 near Wyoming, U.S. 40 near Empire, and I-70 near Vail Pass. Building them will require additional federal funding.

Federal program funds 19 crossings nationwide

The Greenland overpass is one of 19 wildlife crossings that the federal program has funded across the country. Congress created the Wildlife Crossings Pilot Program through the 2021 Bipartisan Infrastructure Law.

The program provides $350 million over five years for these projects nationwide.

California is building the Wallis Annenberg Wildlife Crossing, which will be longer but narrower than Colorado’s structure. Both projects aim to reduce crashes and reconnect habitats that highways have divided.

This article was created with AI assistance and human editing.

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