DEFINITION
An underpass or other crossing method specifically designed to help animals cross roads and highways safely. Often fences will run on either side of the road in order to funnel migrating animals across the wildlife crossing.

AKA
Amphibian tunnels, wildlife passages, wildlife overpass and underpass

PERFORMANCE CRITERIA

UNDERPASS SIZE CLASS	DIMENSION RANGE	FUNCTION	PASSAGE EXAMPLES	SPECIES EXAMPLES
Class 1 - Small	5' high or less	For small terrestrial animals desiring cover	Pipes, Small bridges & dry culverts.	Amphibians, reptiles, & small mammals.
Class 2 - Medium	Box culvert larger than 5' high to 8" by 8'	Allows passages by larger animals; Provides some cover.	Standard box culverts	Small to large carnivores
Class 3 - Large	Box culverts over 8' high & open span bridges	Allows plant growth and stream movement.	Standard box culverts, arch pipes, and bridges.	Large carnivores & ungulates (moose, elk, etc...)
Source: Adapted from www.wildilfeandroads.org

ILLUSTRATION


The diagram below illustrates a typical at-grade wildlife crosswalk. On each side of the highway are an animal detection zone, a detection camera, a flashing light, and wildlife exclusion fencing. When a large animal, such as a moose or elk, steps into the detection zone, the flashing lights warn approaching drivers to slow down. (Source: http://www.tfhrc.gov/pubrds/09septoct/03.htm)


CASE STUDIES
links to separate pages documenting specific places or projects where this element is on display

ADDITIONAL RESOURCES
http://www.fhwa.dot.gov/environment/wildlifecrossings/main.htm - U.S. DOT FHWA, "Critter Crossings"
US DOT Federal Highway Administration- Advances in Wildlife Crossings
Wildlife passages. De-fragmentation in the Netherlands. How to evaluate their effectiveness?