North America’s Largest Wildlife Overpass Is Working: Animal Collisions on I-25 Down 91%.

State wildlife managers and transportation officials in Colorado report that a new wildlife crossing system on Interstate 25 has sharply cut collisions with animals. In the roughly 10 months since the overpass opened between Larkspur and Monument, drivers have hit two animals, a 91% drop. Before the crossings, drivers hit a wild animal about once a day on this stretch between Denver and Colorado Springs.

The $15 million project was completed last December. It includes a 209-by-200-foot bridge, five wildlife underpasses and miles of fencing that guides animals toward the crossings. According to the article, the system gives animals from 700-pound elk to small toads a safer way across six lanes of highway that divide 39,000 acres of habitat. State engineers and wildlife biologists worked together on the design.

From our publisher

Your calendar shouldn't ghost you.

Time blocking built for ADHD brains. Plan, focus, and actually finish.

Start free, no card needed♠Poker Logic Lab

Free chapters: Playing Online Texas Hold'em

The math is the engine. The real skill is reading opponents under uncertainty.

Get the free chapters

Biologists have also used surveys and trail cameras to document smaller animals on the crossings, including rabbits and northern leopard frogs, which have a protected status after population declines. In June, biologists confirmed that a pronghorn crossed the interstate safely for the first time in 20 to 30 years, said Lisa Schwantes of the Colorado Department of Transportation. Tracking data show pronghorn are using the underpasses as well. Bridget O'Rourke of Colorado Parks and Wildlife said, "We are thrilled."

Schwantes said the data point to benefits for drivers too. Fewer crashes mean fewer law enforcement and maintenance workers are needed to divert traffic, and travel delays along the corridor have dropped by about 9%. The department tracks collisions through State Patrol crash reports and through maintenance crews, who log each carcass they remove from the highway.

Six more crossing systems are being designed, including the first overpass built specifically for Rocky Mountain bighorn sheep, on Colorado 40 east of Empire. Other planned sites include westbound I-70 at East Vail Pass, I-25 just north of the New Mexico border, U.S. 160 east of Cortez, Colorado 40 west of Craig, and U.S. 287 south of the Wyoming border.

Starting in January, Colorado drivers will be able to opt in to a $5 fee that goes toward building wildlife crossings. The article notes that a similar $29 fee for the Keep Colorado Wild pass has generated $146 million since 2023.