Collisions between vehicles and wildlife cost California $276 million in 2016, up about 20 percent from the previous year, according to an annual report from the UC Davis Road Ecology Center.

Using state data on over 13,000 traffic incidents during 2015 and 2016, the report maps stretches of California highways that are hotspots for wildlife-vehicle conflicts.

For the report, researchers also mapped the cost per mile of wildlife-vehicle collisions for select highways and estimated the return on investment for installing fencing along those roads to reduce such collisions. For example, the Bay Area’s Interstate 280 is a perennial roadkill hotspot and in 2016 was the state’s worst for collisions with wildlife. The report estimates that building fencing along the highway to prevent wildlife access to the roadway would pay for itself in less than a year with reduced collisions and property damage.  

“We’re seeing an increase in the rate of wildlife-vehicle collisions, and we’re not seeing an increase in our attempt to mitigate the problem,” said Fraser Shilling, co-director of the UC Davis Road Ecology Center. “But this is definitely a problem we can solve. We have the resources and know-how to build solutions that can protect wildlife and drivers.”

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The worst roads

While collisions with wildlife are common throughout the state, they occur most densely in the San Francisco Bay Area, Sierra Nevada foothills, North Coast and parts of the Central and South Coast.

The report ranked highways statewide for severity and cost of wildlife-vehicle collisions in 2015-16. The top 10, listed below, account for about a quarter of the statewide impacts of such collisions:

1. Interstate 280, with 386 collisions over 23 miles. The cost per mile from wildlife-vehicle collisions along this highway is $874,520. The cost of fencing to protect wildlife could pay for itself in about half a year.  
2. U.S. Highway 101 in Marin County, with 225 collisions over 28 miles. Cost per mile is $525,009, with fencing paying for itself in less than a year.   
3. State Route 13, with 81 collisions over 6.5 miles. Cost per mile is $307,218, with fencing paying for itself in a little over a year.
4. State Route 24, with 114 collisions over 11 miles. Cost per mile is $233,567, with fencing paying for itself within less than two years.
5. State Route 174, with 75 collisions over 11 miles. Cost per mile is $216,521, with fencing paying for itself within less than two years.
6. Interstate 680, with 221 collisions over 72 miles. Cost per mile is $193,762, with fencing paying for itself within about two years.
7. State Route 9, with 119 collisions over 20 miles. Cost per mile is $151,995, with fencing paying for itself within about 2.5 years.
8. State Route 2 with 33 collisions over 6 miles. Cost per mile is $144,731, with fencing paying for itself within three years.
9. U.S. Highway 101 at the west end of the San Fernando Valley, with 13 collisions over 26 miles. Cost per mile is $137,735, with fencing paying for itself within three years.
10. U.S. Highway 50 in western El Dorado County with 245 collisions over 54 miles. Cost per mile is $118,692, with fencing paying for itself within 3.5 years.

Underpasses and overpasses across priority highway segments that allow for safe passage of wildlife can also be an effective measure to protect wildlife and drivers from collisions.

The report notes that it does not cover all wildlife-vehicle collisions in the state, only those reported to the California Highway Patrol. Allstate Insurance Co. estimates there were 23,316 claims for collisions with wildlife in 2015-16, which is three times higher than the rate the report describes. If included, it would increase the total cost to society to $500 million per year.

Funding and citizen participation

Individuals interested in submitting roadkill observation information may visit the California Roadkill Observation System website.

The report, produced by the UC Davis Road Ecology Center, was not supported by any external funding.