Colorado’s Greenland wildlife overpass is now the largest in the world

Story: 2025 C.E.  |  Last updated: April 20, 2026

A bridge nearly an acre in size spans six lanes of Interstate 25 south of Denver — and the intended users are elk, pronghorn, and mule deer. Colorado’s Greenland Wildlife Overpass completed construction in December 2025 C.E., becoming the largest wildlife overpass on Earth. It connects fragmented habitat across one of the state’s busiest highways, where large mammals currently face a collision with a vehicle roughly once every single day.

At a glance

• Wildlife overpass: The Greenland structure measures approximately 200 feet wide and 209 feet long — the largest of its kind in the world.
• Habitat connectivity: The crossing links around 39,000 acres of conserved land in Douglas County with more than one million acres of Pike National Forest.
• Collision reduction: As part of an 18-mile network of crossings and fencing along I-25, the project is projected to cut wildlife-vehicle collisions by up to 90 percent.

Why this stretch of highway needed a solution

Interstate 25 between Denver and Colorado Springs cuts directly through land that elk, pronghorn, and mule deer have crossed for generations. The highway didn’t erase those instincts. It just made acting on them deadly.

One collision per day is the current average along this section of I-25. That toll falls on both animals and drivers. Wildlife crossings have a strong track record of reducing those numbers dramatically — studies from transportation agencies across North America consistently show reductions of 80 to 95 percent where crossing infrastructure is paired with guiding fences.

The Greenland overpass is designed with animal behavior in mind. Elk and pronghorn are open-country animals. They avoid confined spaces, which is why tunnels often go unused by large ungulates. An overpass nearly 200 feet wide, covered in native vegetation, reads to these animals as an extension of the landscape — not an obstacle.

A $15 million investment in context

The Colorado Department of Transportation completed the overpass on time and within its $15 million budget. That figure sounds large. But a single serious collision involving a large animal can cost tens of thousands of dollars in vehicle damage, emergency response, and medical care — before counting the animal. Across hundreds of collisions annually, the math shifts quickly.

The overpass is also one piece of a larger system. Eighteen miles of coordinated infrastructure — crossings, underpasses, and directional fencing — channel wildlife toward safe points rather than leaving movement to chance.

Connecting a million acres of wild land

The ecological stakes go well beyond collision statistics. Highways don’t just create danger at the point of crossing — they fracture populations. Animals separated by a busy road can’t interbreed, can’t follow shifting food sources, and can’t respond to drought or fire by moving to new range. Over decades, that isolation reduces genetic diversity and population resilience.

The Greenland overpass stitches together 39,000 acres of conserved land on one side with over a million acres of Pike National Forest on the other. That’s not a minor restoration — it’s a meaningful reconnection of a functioning migration system.

Colorado already has more than 100 wildlife crossing structures statewide. This overpass is its first attempt at bridging fragmented habitat at this scale. It draws on lessons from Banff National Park in Canada, where crossings built in the 1990s have been used by wolves, bears, cougars, elk, and dozens of other species — and have been studied long enough to show real population-level benefits. Similar projects in Utah and elsewhere across the American West have followed Banff’s lead.

There’s also a broader pattern worth noting. Efforts like the Federal Highway Administration’s wildlife crossings program — which has directed hundreds of millions of dollars toward crossing infrastructure since 2022 C.E. — signal that this kind of thinking is moving from niche to mainstream in transportation planning.

What still needs watching

Wildlife crossings work best when the land on either side remains intact. Douglas County is one of Colorado’s fastest-growing areas, and development pressure means the conserved land the overpass depends on could face future fragmentation. The structure itself is fixed. The habitat it connects is not.

There’s also the question of which species actually use it. Elk and pronghorn are the primary targets, but whether mountain lions, black bears, or smaller mammals adopt the structure at meaningful rates will take years of camera trap monitoring to determine. Colorado’s investment is real. What comes next — ecologically and politically — will determine how much of it pays off.

Read more

For more on this story, see: Colorado Department of Transportation

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