The US Rocky Mountain state of Colorado is celebrating a dramatic decline in animal-related car crashes because of the construction of wildlife bridges and underpasses.

From Colorado Department of Transportation

The Colorado Department of Transportation (CDOT) says five underpasses and two overpasses that cross a stretch of highway west of Denver have reduced wildlife related crashes by almost 90 percent.  The state has 30 strategically-located passages, designed with wildlife experts to determine where animals cross the highways.

"We want to make sure that if were going to do it, we're doing it right.  That's why we don't just throw them in everywhere we can," said CDOT wildlife program manager Jeff Peterson to the Denver Post.  "Putting the correct crossing in the correct place for the species you want to get from one place to another - that's where it gets tricky."

Each crossing costs US$300,000 - $1,000,000, so they're not cheap.  But insurance companies damages to vehicles from wildlife collisions averages about $4,000 per incident.  And in a state like Colorado that is rich in wildlife, it adds up very quickly.  On just one highway near Durango, there have been 472 car-animal collisions in the decade from 2006 - 2016.  The 30 well-designed crossings reduce such figures across the state.

From Colorado Department of Transportation

"They're extremely important," Peterson continued.  "When you get into conflicts with wildlife that raises the issue."