North America’s largest wildlife overpass has reduced wildlife collisions by 91% in its first nine months of operation, according to figures from the wildlife mitigation system on Interstate 25 in Douglas County, Colorado.
The 209-by-200-foot crossing spans I-25 near the Greenland exit, between Larkspur and Monument. It forms part of a $15 million project that includes five wildlife underpasses and fencing intended to direct animals towards the crossings.
The structure was designed especially for pronghorn and elk. For decades, I-25 had restricted seasonal animal movement in Douglas and El Paso counties, while the area around the crossing recorded frequent crashes involving wildlife. This section of highway previously saw one deer-vehicle collision per day.
The project is projected to prevent more than 300 highway-speed collisions each year. Reducing these crashes can save human and animal lives, avoid property damage, reduce public service costs and limit traffic delays.
The early collision reduction also points to an unusually fast financial return. The project’s return on investment at this location is estimated at two to three years, compared with a normal 15-year return on investment for wildlife crossings.
Each avoided wildlife-vehicle collision can save more than $19,000 in a deer crash. The estimated saving is $73,000 for an elk collision and $110,000 for a moose collision. Attardo said wildlife overpasses generally pay for themselves in about 15 years through the accidents they prevent.
Wildlife-vehicle crashes cause approximately 200 deaths and 26,000 injuries nationwide each year, with costs of more than $8 billion. The Colorado results come from a high-collision location and cover only the first nine months after the overpass opened.
There is no figure yet for the number of animals documented using the Colorado overpass, or for the species making the crossings. Long-term data will be needed to establish whether the 91% reduction continues over time.
Other projects have also recorded results after crossings were built. A wildlife overpass in Washington has reached 10,000 documented safe crossings over Interstate 90 at Snoqualmie Pass. In the stretch of I-90 at Snoqualmie Pass containing the overcrossing and undercrossings, the number of carcasses has fallen to nearly zero.
According to the Pew Charitable Trusts, wildlife crossing infrastructure can reduce deer and elk collisions by up to 97%. The Colorado system combines an overpass, underpasses and fencing in an effort to restore routes that had been fragmented by I-25 while reducing the risks faced by drivers and animals.
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