A grass-covered bridge spanning six lanes of a busy US highway is helping wildlife cross safely between habitats, while a wider network of crossings and fences has cut animal-vehicle collisions by 91% along a stretch of Interstate 25 in Colorado.
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network → cover → Colorado
The Greenland Wildlife Overpass, completed in December 2025, connects 39,000 acres of habitat near Larkspur and Monument, south of Denver.
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Overpass → complete → Denver
The $15 million structure is designed primarily for large animals such as elk and pronghorn, which often avoid enclosed tunnels.
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which → design → tunnels
It forms part of an 18-mile wildlife-mitigation system that also includes five underpasses and fencing to guide animals away from traffic.
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that → form → traffic
State officials say the results offer a promising example of how road infrastructure can protect wildlife while making highways safer for motorists.
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highways → say → motorists
Colorado's giant green wildlife bridge over Interstate 25
The Greenland Wildlife Overpass is located near the Greenland interchange in Douglas County, between Larkspur and Monument.
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Overpass → locate → Larkspur
Built by the Colorado Department of Transportation (CDOT), it spans six lanes of Interstate 25, a major route connecting Denver and Colorado Springs.
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it → build → Denver
The bridge measures 200 feet wide and 209 feet long, covering approximately 41,800 square feet.
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bridge → measure → feet
Its surface is layered with soil and vegetation, while its broad, gradually sloping entrances are designed to encourage animals to approach and cross naturally.
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entrances → layer → animals
The structure was completed in December 2025, closing a 3.7-mile gap between existing wildlife crossings along the highway.
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structure → complete → highway
It connects habitats used by elk, pronghorn, mule deer, black bears and other animals.
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It → connect → elk
According to CDOT, the crossing forms part of a wider network designed to reduce wildlife-vehicle collisions and maintain movement between natural habitats separated by the interstate.
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crossing → accord → interstate
Wildlife-vehicle collisions fell by 91%
A state-commissioned study found that wildlife-vehicle collisions along the I-25 South Gap corridor fell by 91% in the final year of the study period.
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collisions → fall → period
The reduction followed the installation of most of the area's wildlife-mitigation infrastructure, including underpasses and fencing.
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reduction → follow → underpasses
The corridor previously experienced an average of about one wildlife-vehicle collision per day during periods of high animal movement in spring and autumn.
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corridor → experience → spring
Seasonal migrations bring animals across the landscape as they move between feeding areas and other parts of their ranges.
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they → bring → ranges
The research examined collision trends from 2022 to 2024.
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research → examine → 2024
During that period, the average annual reduction was approximately 85%, reaching 91% in the final year.
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reduction → reach → year
The findings indicate that the wider crossing system has significantly improved safety.
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system → indicate → safety
However, the overpass itself was completed in December 2025, after the study period, so the 91% figure cannot be attributed solely to the new bridge.
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figure → complete → bridge
Why elk and pronghorn need a bridge instead of a tunnel
Large animals such as elk and pronghorn can be reluctant to enter enclosed passages.
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animals → need → passages
Tunnels may restrict their sightlines and movement, while the size of an animal's antlers can make narrow structures particularly unsuitable.
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structures → restrict → antlers
The Greenland overpass offers a broad, open route across the highway.
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overpass → offer → highway
Its vegetation-covered surface and gradual approaches are intended to resemble the surrounding landscape, making the crossing more inviting to animals.
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crossing → cover → animals
The wider system complements the bridge with five underpasses that provide alternative routes for wildlife, including smaller species.
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that → complement → species
Fencing along the highway helps guide animals towards these designated crossings rather than allowing them to enter traffic lanes.
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them → help → lanes
Together, the measures address two related problems: the risk of collisions and the fragmentation of habitats by major roads.
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measures → address → roads
Elk and pronghorn have begun using the crossing
Wildlife cameras have recorded elk herds crossing the overpass, providing early evidence that the structure is being used by the animals it was designed to accommodate.
Pronghorn have also been filmed crossing to the western side of I-25.
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Pronghorn → begin → I-25
State officials have described these sightings as particularly significant because the highway had long restricted their movement through the area.
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highway → describe → area
Monitoring has also recorded smaller wildlife, including rabbits and northern leopard frogs, using the crossing area.
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Monitoring → record → area
The project includes features intended to provide smaller animals with shelter from predators while they move across the exposed bridge.
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they → include → bridge
These observations show that the structure is functioning as a wildlife passage.
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structure → show → passage
Researchers are continuing to investigate whether it will also help reconnect animal populations that have been separated by the highway.
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that → continue → highway
The $15 million project connects 39,000 acres of habitat
The Greenland overpass cost $15 million to construct, with federal funding providing the bulk of the support through the US Department of Transportation's Wildlife Crossings Pilot Program.
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funding → connect → Program
The project was developed through cooperation between CDOT, the Federal Highway Administration, Colorado Parks and Wildlife, Douglas County and conservation partners.
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project → develop → CDOT
The crossing connects approximately 39,000 acres of habitat on either side of I-25, with the surrounding wildlife landscape linked to more than one million acres of the Pike National Forest.
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landscape → connect → Forest
The overpass also completes a wildlife-crossing network along an 18-mile section of the interstate between Castle Rock and Monument.
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overpass → complete → Rock
More than 100,000 vehicles travel through this corridor each day, making the separation between road traffic and animal movement an important safety concern.
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separation → travel → traffic
Researchers will study whether the bridge reconnects wildlife populations
Reducing collisions is only one measure of the project's success.
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Reducing → study → success
Researchers also want to understand whether the crossings help animals move between previously separated populations and whether that movement improves genetic diversity over time.
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movement → want → time
…and 5 more, not listed.
The Aporia
