Effectiveness of wildlife underpasses and fencing to reduce wildlife-vehicle collisions

Published source details McCollister M.F. & van Manen F.T. (2010) Effectiveness of wildlife underpasses and fencing to reduce wildlife-vehicle collisions. Journal of Wildlife Management, 74, 1722-1731.
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This study is summarised as evidence for the following.

	Action	Category
	Install one-way gates or other structures to allow wildlife to leave roadways Action Link
	Install barriers and crossing structures along roads/railways Action Link
	Install barrier fencing and underpasses along roads Action Link

Install one-way gates or other structures to allow wildlife to leave roadways

A replicated, controlled study in 2000–2007 along a highway in North Carolina, USA (McCollister & van Manen 2010) found that barrier fencing with escape gates and underpasses facilitated road crossings by a range of mammals but did not reduce road casualties. A similar rate of mammal road casualties was recorded over one year on road sections with fencing, escape gates and underpasses (5.0/km) as on sections without (5.1/km). A four-lane highway was constructed with three underpasses. Barrier fencing, 3 m high, was installed ≥800 m along the highway from each underpass. Gates allowed trapped animals to escape the highway. Road deaths were recorded along 6 km of road with fencing and underpasses and 11 km without, twice/week, from July 2006–July 2007.

(Summarised by: Rebecca K. Smith)
Install barriers and crossing structures along roads/railways

A replicated, site comparison study in 2006–2007 on a highway through forest and agricultural land in North Carolina, USA (McCollister & van Manen 2010) found that fenced stretches of road with underpasses tended to have lower rates of reptile road mortality than those without. Results were not statistically tested. Reptile mortality on stretches of road with underpasses and fencing was 1 reptile/km (8 individuals) compared to 2 reptiles/km (26 individuals) on unfenced road with no underpasses. Some reptiles, e.g. snakes, were small enough to climb through the fencing (see original paper). A new four-lane highway was constructed in 2001–2005 with three underpasses (3 m high, 29–47 m wide). Each underpass had an 800 m fence either side of it, which ran parallel to the highway, then continued under the underpass and connected with fencing on the opposite side (3 m high chain-link fencing). A section of the highway (with underpasses and fencing 6,375 m; without: 10,873 m) was surveyed for wildlife casualties twice/week in July 2006–July 2007.

(Summarised by: Katie Sainsbury)
Install barrier fencing and underpasses along roads

A site comparison study in 2000–2007 along a highway in North Carolina, USA (McCollister & van Manen 2010) found that underpasses and barrier fencing facilitated road crossings by a range of mammals but did not reduce road casualties. Camera traps showed crossings through the three underpasses by white-tailed deer Odocoileus virginianus (2,258 times), raccoon Procyon lotor (125), American black bear Ursus americanus (15), bobcat Lynx rufus (11), gray fox Urocyon cinereoargenteus (eight), Virginia opossum Didelphis virginiana (six), rabbits Sylvilagus spp. (two) and Canis spp. (two). Track counts indicated an additional 3,552 mammal crossings by 15 species, with 90% by white tailed deer. A similar number of mammals was killed over one year on road sections with underpasses and fencing (5.0/km) as on sections without (5.1/km). A four-lane highway was constructed with three underpasses. Barrier fencing, 3 m high, was installed ≥800 m along the highway from each underpass. Gates allowed trapped animals to escape the highway. Underpass use was monitored by 2–3 camera traps /underpass. Twice-weekly track surveys were conducted (on 2.5-m-wide plates across underpasses). Road deaths were recorded along 6 km of road with fencing and underpasses and 11 km without, twice/week, from July 2006–July 2007.

(Summarised by: Rebecca K. Smith)