Underpasses for Animals Can Make Roadways Safer for Cars and Wildlife

Newswise — Design features such as overpasses keep drivers moving safely on our highways, letting cars pass in different directions without interacting with other cars or trains. Allowing wildlife to move from one side of the road to the other without encountering vehicle traffic is a challenge for transportation planners and wildlife managers. As transportation networks continue to expand, a similar solution may help avoid wildlife–vehicle collisions.

A study reported in the current issue of The Journal of Wildlife Management rates the effectiveness of highway underpasses for wildlife. Researchers found that the cost of building these underpasses in the highway proved to be a savings of property and life.

Collisions between wildlife and vehicles can cause substantial damage to vehicles and injure—or even kill—people. Wildlife doesn’t fare much better. High mortality due to vehicles can affect the viability of some small populations of animals.

A new route planned for U.S. Highway 64 in Washington County, North Carolina, gave researchers the opportunity to document wildlife activity both before and after the road was built. The new route cut through a forested and agricultural area, bringing together cars and resident animals such as black bears, red wolves, and white-tailed deer. Part of the highway construction included three underpasses with fencing running alongside the roadways near each underpass to “funnel” the animals through.

With the use of multiple cameras and surveys of animal tracks, researchers counted wildlife activity both in the planning and construction stages of the highway and after it was completed and open to traffic. Before road construction, the cameras captured 242 instances of deer passing through the area where the underpasses would be. During a 13-month period after construction, 2,433 photographs of various animals, primarily deer, but also bears, raccoons, and domestic dogs and cats, were taken as they used the underpasses. Animal deaths from vehicle collisions were counted as well.

When compared with reports from adjacent sections of U.S. Highway 64, the new section of road experienced approximately a 58% reduction in wildlife mortality. This suggested a favorable cost–benefit analysis for building the underpasses.

Improvements to further reduce wildlife–vehicle collisions include continuous fencing along roads rather than small sections, higher fences, and fences dug into the ground to prevent smaller animals from going underneath. Drainage culverts placed at more frequent intervals, rather than larger underpasses built farther apart, could provide a more economical way to allow animals to pass under the road.

Full text of the article, “Effectiveness of Wildlife Underpasses and Fencing to Reduce Wildlife–Vehicle Collisions,” The Journal of Wildlife Management, Vol. 74, No. 8, 2010, is available at http://www2.allenpress.com/pdf/JWM-74-8-1722_1731.pdf

About The Journal of Wildlife ManagementThe Journal of Wildlife Management, published since 1937, is one of the world’s leading scientific journals covering wildlife science, management, and conservation. It is published eight times per year by The Wildlife Society. To learn more about the society, please visit: http://joomla.wildlife.org/.