Just north of Larkspur, Colorado, a stretch of Interstate 25 carries over **100,000 vehicles** every single day. For decades, it also carried a grim, daily toll: an average of **one wildlife collision per day** during migration seasons, as elk, pronghorn, mule deer, and other animals tried to cross one of the busiest highways in the American West.
In December 2025, that changed.
The **I-25 Greenland Wildlife Overpass** opened to wildlife — and at **200 feet wide** and **209 feet long**, covering nearly **41,800 square feet** of surface area, it is officially the **largest wildlife overpass in North America**, and one of the largest in the world.
**Built for Elk, Not Humans**
Every engineering decision in the Greenland overpass was made with large ungulates in mind. Traditional wildlife crossings are often narrow — tunnel-like structures that animals with a flight instinct avoid entirely. Elk and pronghorn, in particular, resist enclosed spaces. They need to see where they're going.
The Greenland overpass solves this with design:
🦌 **Gradual, wide-sloping entrances** that give approaching animals a clear, unobstructed sightline across to the other side 🌿 **Native vegetation planted across the entire surface** to make the crossing look and feel like natural terrain 🏔️ **Berms and plantings along the edges** to screen out traffic noise, light, and the visual disturbance of passing vehicles 📐 **200-foot width** — approximately the length of two-thirds of a football field — providing animals with space to spread out and reduce crowding stress
The result is a structure that, from an elk's perspective, reads less as a bridge and more as a meadow that happens to cross above a roaring highway.
**The Habitat Problem It Solves**
The I-25 corridor through Douglas County bisects one of Colorado's most critical wildlife migration routes. On either side of the highway lie **39,000 acres of connected wildlife habitat** — the Greenland Open Space on the west and the Pinon Valley Park on the east — used by elk, mule deer, black bears, mountain lions, pronghorn antelope, and numerous smaller species that depend on seasonal movement between ranges.
Before the crossing, that movement was severed. The animals either risked the highway — often fatally, and often for the humans involved too — or their movement was constrained, limiting access to water, grazing land, and mates across the seasonal range.
The overpass restores what the highway cut: a continuous corridor that allows animals to move the way their biology requires.
**Ahead of Schedule, Under Budget**
The project was delivered by the **Colorado Department of Transportation (CDOT)** in December 2025, **ahead of schedule and under budget** — a combination that has become something of a calling card for Colorado's wildlife infrastructure programme.
The Greenland crossing is part of a broader system along this stretch of I-25 that also includes multiple underpasses and strategic fencing designed to funnel animals toward safe crossing points and away from open highway. Before the complete system, the statistics were stark: one collision per day during migration seasons. The estimated reduction with the full system in place: **90 percent fewer wildlife-vehicle incidents** on this section of road.
That means safer roads for drivers and safer passage for animals — simultaneously.
**A Growing Movement**
Colorado's Greenland overpass doesn't stand alone. Across North America, wildlife crossings are proliferating as the science of connectivity ecology — the study of how animals move through landscapes — has matured into infrastructure policy.
In Southern California, the **Wallis Annenberg Wildlife Crossing** over the 101 Freeway near Los Angeles is nearing completion in 2026 — designed to reconnect mountain lion populations separated by urbanisation for decades. In Canada, wildlife crossings along the Trans-Canada Highway through Banff National Park have been operating for over two decades, with documented use by wolves, grizzly bears, cougars, and hundreds of thousands of large ungulates.
The data from established crossings is unambiguous: animals use them, wildlife-vehicle collisions drop, and populations on either side begin to genetically reconnect. The only question has ever been whether the political will and funding could match the scientific evidence.
In Colorado, the answer has been yes.
**What Comes Next**
CDOT and conservation partners are already tracking animal use of the Greenland overpass through camera traps and GPS-collared elk. The warm December of 2025 meant early usage was modest — animals weren't in full migration mode — but as spring migration begins in 2026, wildlife biologists expect to see the crossing come into full use.
North America's largest wildlife bridge is ready. The elk will find it. 🦌🏔️🌿
*Sources: Colorado Department of Transportation (CDOT) · Colorado Governor's Office · CPR News · CBS News Colorado · Wildlife Society · Cowboy State Daily · December 2025*
