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Providing evidence to improve practice

Individual study: Highway mitigation fencing reduces wildlife-vehicle collisions

Published source details

Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicle collisions. Wildlife Society Bulletin, 29, 646-653


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Install overpasses over roads/railways Terrestrial Mammal Conservation

A replicated, before-and-after study in 1981–1999 in temperate mixed woodland and grassland in Alberta, Canada (Clevenger et al. 2001) found that wildlife overpasses, underpasses and roadside barrier fencing reduced road deaths of large mammals. Species recorded as road casualties included coyote Canis latrans, black bear Ursus americanus, wolf Canis lupus, bighorn sheep Ovis Canadensis, moose Alces alces, deer Odocoileus spp. and elk Cervus canadensis. Mammal-vehicle collisions were significantly lower during the two years after fencing (5–28/year) compared to the two years before (18–93/year) for all three road sections, despite an increase in traffic flow. Ungulate casualties declined by 80%. Most road deaths were within 1 km of the end of the fences. Deaths also occurred close to drainage structures. The Trans-Canada highway was expanded to four lanes and had 2.4-m-high wildlife exclusion fence installed in three phased sections, completed in 1984 (10 km), 1987 (16 km) and 1997 (18 km). In addition, 22 wildlife underpasses and two overpasses were constructed. Wildlife-vehicle collisions were monitored from May 1981 to December 1999.

(Summarised by Rebecca K. Smith)

Install barrier fencing and underpasses along roads Terrestrial Mammal Conservation

A before-and-after study in 1981–1999 in temperate mixed woodland forest and grassland in Alberta, Canada (Clevenger et al. 2001) found that underpasses and overpasses, along with roadside fencing, reduced road deaths of large mammals. Wildlife-vehicle collisions were significantly lower during the two years after fencing (5–28/year) compared to the two years before (18–93/year) for all three road sections, despite an increase in traffic flow. Ungulate casualties declined by 80%. Species included coyote Canis latrans, black bear Ursus americanus, wolf Canis lupus, bighorn sheep Ovis Canadensis, moose Alces alces, deer Odocoileus spp. and elk Cervus canadensis. Most road deaths were within 1 km of the end of the fences. Deaths also occurred close to drainage structures. The Trans-Canada highway was expanded to four lanes and had 2.4-m-high wildlife exclusion fence installed in three phased sections, completed in 1984 (10 km), 1987 (16 km) and 1997 (18 km). Twenty-two wildlife underpasses and two overpasses were constructed along these sections. Wildlife-vehicle collisions were monitored from May 1981 to December 1999.

(Summarised by Rebecca K. Smith)