US Highway 93 Wildlife Overpasses: Promoting Highway Permeability and Safety for Desert Bighorn Sheep

Three wildlife overpasses and adjacent funnel fencing were constructed along United States Highway 93 (US93) to promote habitat connectivity for bighorn sheep and reduce wildlife-vehicle collisions. The project team spent two years monitoring GPS data for sheep distribution and trans-highway movements before construction. Crossing features included three wildlife overpasses with 7- to 8-foot-high exclusionary fencing to guide sheep to the overpasses and to additional drainage structures (three culverts and the dry washes under two bridges). The construction reduced sheep-vehicle collisions by 97 percent from preconstruction figures and helped sheep move across habitats to maintain genetic diversity.