Protecting Wildlife and Motorists through Infrastructure Design

Editor’s Note: This article first appeared as NMA E-Newsletter #625. If you would like to receive the weekly newsletter via email, subscribe today!

Several states have recently announced that they have added wildlife over and underpasses, with many more on the way. Large animals such as deer, elk, and bears roam seasonally, frequently colliding with vehicles in the process. In Wyoming, for example, there are 6,000 documented collisions annually. Wildlife managers and transportation engineers use infrastructure design to help prevent wildlife-vehicle collisions. As a unique and indispensable tool for accident prevention, this kind of infrastructure also helps reestablish biological connectivity for herds.

The benefit is not just for animals but motorists too. Not only can a collision with a large animal total your car, but it will also likely kill the animal and could put your life or your passenger’s in mortal danger.

State Farm estimates that between July 1, 2019, and June 30, 2020, there were over 1.9 million animal-collision insurance claims in the US. According to a recent company study, new data show US drivers have a 1 in 116 chance of a collision with wildlife.  Most of the time, collisions occur at dusk or during the night in October, November, and December.

Overpasses are expensive to build. In Wyoming, two-lane road structures cost between $6 to 14 million. An interstate overpass is even more expensive, typically in the $20 to $30 million range. That is why the Wyoming Game and Fish Department and WYDOT only recommend these structures when justified and suited to the species and location. Other lower-cost options include using existing underpasses, slowing night-time speed limits, posting more visible “wildlife present” warning signs, and improving sightlines by keeping rights of way mowed and clear of trees and brush.

Data and other on-the-ground conditions must support any road modifications. Sometimes the data include decades of research on how big game such as deer, elk, moose, or pronghorn migrate. When animal bypasses are appropriately located, they have proven to be 80 to 90 percent effective in reducing collisions.

Credit: Veronika Ronkos

In Utah, a video was released showing how successful a wildlife overpass over Interstate 80 has become. Three-and-a-half miles of fencing guide wildlife to the overpass that crosses above six lanes of traffic. This overpass is 50 feet wide and 320 feet long. In the last two years, cameras on the bridge have captured herd animals plus black bears, bobcats, cougars, coyotes, and smaller animals like yellow-bellied marmots and porcupines crossing the bridge. This overpass came online in 2018, but in the two years before completion, Utah DOT recorded 106 collisions with wildlife, including 98 deer and three moose.

Most of these bridges are for wildlife only. In San Antonio, Texas, the city has built a human-animal natural bridge between two sections of a city park. City officials claim it is the longest bridge of this kind in the US. The Robert L.B. Tobin Land Bridge stretches over a six-lane highway and connects two sections of the 330 acre Phil Hardberger Park, named after a former mayor. The overpass has been a public-private partnership with $10 million in private donations added to $13 million from a bond approved by voters in 2017.

Recently in Colorado, the Interstate Highway 25 South Gap project added two wildlife underpasses at the Greenland Road and I-25 Interchange. Both are 100 feet wide by 18 feet tall and will hopefully prove to be highly effective at minimizing animal-vehicle interactions. The Colorado DOT plans to add two more in the area with the hope of reducing such accidents by 90 percent.

Credit: Tony Webster

Another planned wildlife overpass is the 200 foot-long Liberty Canyon Wildlife Crossing stretching over the 101 Freeway in Los Angeles. This bridge is expected to be finished in the next five years. Many migrating animals have lost their natural range because they cannot easily cross the intimidating highway. The planned bridge will benefit all wildlife in the area and, in particular, mountain lions who face isolation in the Santa Ana and Santa Monica Mountains and possible extinction.

Protecting wildlife protects motorists in the end. Safety comes with a price tag. Not taking appropriate measures has a bigger one.

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One Response to “Protecting Wildlife and Motorists through Infrastructure Design”

  1. GW says:

    Interesting. It would seem that underpasses would be less expensive than the elaborate huge overpasses that I have seen constructed in recent years.