Colorado wildlife overpass, North America’s largest, opens to help animals cross highways safely

Wildlife in Colorado now has a safer route across one of the region’s busiest highways. A newly finished green overpass spanning Interstate 25 near Larkspur gives elk, pronghorn, moose, bears and mountain lions a natural corridor to move between habitats without risking collisions with traffic.

Built faster than planners expected and within its budget, the structure completes a broader network of crossings intended to reconnect fragmented habitat and dramatically cut the number of wildlife-vehicle incidents along the I-25 corridor between Larkspur and Monument.

What the Greenland overpass is and why it matters for wildlife safety

The Greenland overpass is a broad, vegetated bridge that allows animals to cross six lanes of interstate traffic without encountering cars. At the heart of a larger effort known as the I-25 South Gap Project, the overpass links roughly 39,000 acres of habitat on both sides of the highway and is designed to handle wide-ranging species that need more space to pass.

• Size: 200 feet wide and 209 feet long—about 41,800 square feet (3,900 square meters).
• Structure: Supported by 76 girders that uphold a planted deck so animals can move naturally across the span.
• Traffic below: The overpass sits above a stretch used by roughly 100,000 vehicles per day.
• Purpose: Specifically engineered for large ungulates like elk and pronghorn, but also used by bears, mountain lions, deer and smaller mammals.

How the crossing was built and funded

Construction wrapped up in December after under-a-year work that stayed on schedule and on cost. The project was made possible by a multi-agency public-private partnership, with technical support from state and federal transportation agencies. The majority of the construction funding came from a federal initiative aimed at wildlife safety: the Wildlife Crossings Pilot Program.

• Final construction cost: approximately $15 million.
• Partners included the Colorado Department of Transportation, Colorado Parks and Wildlife, and the Federal Highway Administration, among others.

Design features aimed at encouraging animal use

Planners covered the bridge deck with soil and native vegetation so animals perceive it as a natural passage rather than a man-made structure. The overpass complements five underpasses along the 18-mile I-25 corridor near Castle Rock, creating a connected system of routes for migration and daily movements.

Built for a variety of species

Design choices focused on allowing both large and small species to cross safely:

• Wide, vegetated surface for elk, pronghorn and moose.
• Multiple underpasses and passageways that are already showing use by smaller mammals.
• Landscape continuity to reduce hesitation and encourage natural migration patterns.

Expected impact on collisions and wildlife movement

State transportation and wildlife agencies expect the crossing system to cut wildlife-vehicle collisions by a significant margin. Officials have projected up to a 90% reduction in collisions along this corridor, far lowering the daily risk that once surged during spring and fall movement periods—when the area previously saw about one wildlife-vehicle crash per day on average.

Early monitoring of the companion underpasses indicates that both big and small mammals are already using the alternative routes, a promising sign for the overpass itself once animal movement patterns adjust.

Voices from state leaders and wildlife managers

State leaders framed the overpass as both a safety upgrade and a conservation milestone. The governor praised Colorado’s investment in reducing collisions and protecting wildlife habitat for future generations. Transportation and wildlife officials highlighted that years of planning and collaboration went into the project and emphasized their optimism that the structure will restore migration pathways that I-25 once severed.

Wildlife managers expect deer, elk, bears, mountain lions and other species to begin using the overpass regularly, helping to reconnect populations and reduce road mortality.

Where this fits into a growing national effort

The Greenland overpass is now the largest wildlife bridge in North America and ranks among the biggest worldwide. Its completion joins a growing roster of high-profile wildlife crossings—from Utah to Los Angeles—that aim to keep animals off busy roadways and prevent deadly collisions.

• Complements smaller crossings along the I-25 South Gap Project.
• Serves as a model for future crossings in other states and urban corridors.

Watch and share: public resources and media coverage

Local media outlets have captured aerial footage and time-lapse video of the steel-and-soil structure being topped with vegetation, and state agencies are publishing monitoring updates as animals begin to explore the new route. Social channels and news stations offer videos demonstrating the bridge and explaining how the system is expected to reduce collisions and reconnect habitat.

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Michael Thompson

Michael Thompson is an experienced journalist covering U.S. and global news. With ten years on the front lines, he breaks down political and economic stories that matter. His precise writing and keen attention to detail help you grasp the real‑world impact of every event.