The Grass Bridge
A pronghorn crossed Interstate 25 on a new grass bridge, the first in decades. Drivers have hit two animals in ten months. The famous 91 percent figure belongs to an earlier phase.
A pronghorn crossed Interstate 25. The bridge had been waiting decades.
Between Denver and Colorado Springs, Interstate 25 used to work like a wall. On the stretch between Larkspur and Monument, drivers hit about one wild animal a day. In December 2025 Colorado opened a grass-covered bridge over those six lanes. Officials call it North America's largest wildlife overpass. The deck is 209 by 200 feet. Five underpasses and miles of 8-foot fence funnel animals toward it. On the far side is 39,000 acres of habitat that the highway had cut in two.
In June, a camera caught a pronghorn on the bridge. Lisa Schwantes of the Colorado Department of Transportation said it was the first confirmed crossing of that interstate by the species in 20 to 30 years. Pronghorn had spent those decades walking the fence, looking for a gap wide enough to trust. Elk, bears, mule deer, coyotes, rabbits, northern leopard frogs and the threatened Preble's meadow jumping mouse have used the corridor too.
In the roughly ten months since the bridge opened, state wildlife managers and transportation officials told The Colorado Sun that drivers have hit two animals. The project was budgeted at about $30 million and finished for $15 million. Chuck Attardo, CDOT's environmental manager, said elk and pronghorn want a deck they can see across. A dark culvert is not that.
The cold open is the animal on the grass. The number two comes second. The fight over what "91 percent" refers to comes last, and it comes as a limit, not a boast.
Key Facts
- Overpass opened December 2025, I-25 between Larkspur and Monument
- Deck 209 by 200 feet; five underpasses; 8-foot fencing
- Connects 39,000 acres
- Two reported wildlife-vehicle collisions in about 10 months, against about one animal a day before
- First pronghorn crossing of this stretch in 20 to 30 years, confirmed June 2026
- Built for $15 million against a $30 million budget ($22 million federal, $8 million state)
- Colorado Sun, 14 October 2026; The Guardian, 19 October 2026
Why This Matters
A highway that kills an animal a day is a design failure, not a fact of nature. The fix is specific: a wide open deck, fencing that leads to it, and underpasses for the animals that will not take the high road. CDOT says it will site the same system where the crash data justify the cost. That is a method, not a monument.
What We Don't Know Yet
Whether the 91 percent figure that keeps getting attached to this bridge belongs to the bridge. A CDOT study covering 2022 through 2024, discussed by Colorado Politics and Threatened Colorado, measured the underpasses and fencing built before the overpass opened, and found a drop of that size in that earlier window. The Sun's "two collisions in ten months" is the number tied to the period since the deck opened. We have not seen the raw crash table. Two collisions is not zero, and ten months is not a decade.