California studying a highway-topping wildlife bridge to keep cougars out of traffic

Environment Transportation Urbanism West
Proposed wildlife crossing infrastructure. (Courtesy Resource Conservation District)

Proposed wildlife crossing infrastructure. (Courtesy Resource Conservation District)

A car driving on a section of Interstate 5 just north of Los Angeles struck a mountain lion named P-32 one early morning this past summer. The cat was once of a small population that has been tracked roaming Southern California wilderness areas. The death, while reported as “sad, but unsurprising,” drew attention to the close proximity of these animals. Our transportation and urban infrastructures draw unnatural lines through their natural habitats.

Earlier this month Caltrans released a proposal for a landscaped bridge across the 101 Freeway. A 165-foot-wide, 200-foot-long overpass would provide safe passage for wildlife from the Santa Monica Mountains to the Simi Hills and Santa Susana Mountains, an area that has seen rapid development in recent decades. According to the Liberty Canyon Wildlife Crossing project study report, biologists National Park Service have counted a dozen mountain lion deaths in the area since 2002.


Habitat map of L.A.’s mountain lion population. (Courtesy Save LA Cougars)

The wildlife crossing is an ambitious piece of infrastructure. Not only does it have to span 10 lanes of traffic, the bridge needs to be amenable to the pumas, foxes, bobcats, and coyotes it wants to serve. As such, the more than $30 million dollar bridge would be landscaped with native, drought-tolerant vegetation mimics the natural habitat. Barriers would muffle noise and block bright headlights.

The released project study report was funded by a $1 million grant by the State Coastal Conservancy. An additional $3 million is being sought to continue the development of the final design plans.

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