Colorado's new wildlife overpass slashes animal-vehicle crashes by 91% on I-25

Colorado began constructing a wildlife crossing network in 1996 to address the barrier created by Interstate 25, which carries over 100,000 vehicles daily between Castle Rock and Monument. The program now comprises about 14 miles of fencing, five underpasses and a newly completed $15 million overpass that spans six lanes, measuring roughly 200 feet wide and 209 feet long. After most of the infrastructure was in place, reported wildlife-vehicle collisions along the 18-mile corridor fell about 85% between 2022 and 2024 and reached a 91% reduction in the final year of the study.

Only two wildlife-related crashes have been logged since the overpass opened, while cameras have captured elk, pronghorn, rabbits, northern leopard frogs and threatened meadow-jumping mice using the structure. Fewer crashes also mean fewer traffic delays and lower emergency-response costs. Building on this success, Colorado plans six additional crossing projects, including one designed for bighorn sheep, to further reconnect habitats and improve road safety.