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Joseph A. Burns CWB
National Threatened and Endgangered Species Program Leader
Watershed, Fish, Wildlife, Air, Rare Plants
1400 Independance Ave SW - MS1121
Washington, D.C. 20250-1121
(202) 205-0919


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Common Types of Wildlife Crossing Structures

Wildlife crosses OVER the traffic.

Wildlife Overcrossing
A grade separation structure designed to allow wildlife to cross over an intersecting roadway. It is usually covered with vegetation. Also called ecoduct, wildlife bridge, green bridge, biobridge, or wildlife overpass. The largest overcrossings may be called landscape connectors.
Wildlife Overcrossing
The roadway bores through a substantial amount of earth, allowing undisturbed vegetation and soil on top.


Wildlife Crosses UNDER the traffic.

Animals pass under an intersecting roadway through a bridge. A bridge forms part of the roadway and is usually at least 20’ long.

Single span bridge
The structure rests on abutments with no intermediate support columns. Also calledopen span bridge.
Single span bridge
Multiple span bridge
One or more intermediate support columns between abutments.
Multiple span bridge
Long, multiple-span bridge
Same as viaduct, only often over wetlands.


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Page Last Modified: July 21, 2015