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Providing evidence to improve practice

Individual study: Warning signs mitigate deer–vehicle collisions in an urban area

Published source details

Found R. & Boyce M.S. (2011) Warning signs mitigate deer–vehicle collisions in an urban area. Wildlife Society Bulletin, 35, 291-295


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

Install signage to warn motorists about wildlife presence Terrestrial Mammal Conservation

A replicated, randomized, controlled, before-and-after study in 2005–2008 at 26 urban sites around a city in Alberta, Canada (Found & Boyce 2011) found that warning signs reduced the number of collisions between vehicles and white-tailed deer Odocoileus virginianus. At warning sign locations, there were fewer deer-vehicle collisions after sign installation (0.4 deer-vehicle collisions/location/year) than before (1.7 deer-vehicle collisions/location/year). Concurrently, at locations without warning signs, there was no significant difference in deer-vehicle collision rates after (1.0 deer-vehicle collisions/location/year) compared to before signs were installed (1.7 deer-vehicle collisions/location/year). Twenty-six road locations with high incidence of deer-vehicle collisions were selected. Pairs of reflective deer warning signs (90 × 90 cm, diamond shape) were mounted on 3-m-high posts, 1,600 m apart, facing opposite directions, at 13 locations (randomly selected) in June 2008. The other 13 locations had no signs installed. Deer carcasses (mostly white-tailed deer but possibly some mule deer Odocoileus hemionus) were monitored within an 800-m radius of each location from June to December in 2005–2007 (before sign installation) and in June–December 2008 (after sign installation).

(Summarised by Ricardo Rocha)