Effectiveness of temporary warning signs in reducing deer-vehicle collisions during mule deer migrations

  • Published source details Sullivan T.L., Williams A.F., Messmer T.A., Hellinga L.A. & Kyrychenko S.Y. (2004) Effectiveness of temporary warning signs in reducing deer-vehicle collisions during mule deer migrations. Wildlife Society Bulletin, 32, 907-915.


This study is summarised as evidence for the following.

Action Category

Install signage to warn motorists about wildlife presence

Action Link
Terrestrial Mammal Conservation
  1. Install signage to warn motorists about wildlife presence

    A replicated, controlled, before-and-after study in 1995–2002 along five highways in Utah, Nevada and Idaho, USA (Sullivan et al. 2004) found that temporary warning signs reduced vehicle speeds and collisions with mule deer Odocoileus hemionus during migrations. Fewer deer deaths occurred after signs were installed (3–12/migration) than before (7–35/migration). Concurrently, deaths did not decline on a road section without signs (after: 3–13/migration; before: 3–11/migration). Once signs were installed, the proportion of vehicles speeding (8%) was lower than before they were installed (19%). There was no concurrent decline on a road section without signs (after: 19%; before: 25%). Signs affected speeds of heavy trucks more than of passenger vehicles. Sections of five highways, crossed by mule deer seasonal migrations, were studied. Each 6.5-km-long section was divided into two with each half randomly assigned as treatment or control. Treatment sections had temporary yellow and black warning signs (2 × 1 m) with reflective flags and solar-powered flashing amber lights installed at each end and smaller signs (1 m²) each mile. Deer-vehicle collisions were monitored daily during spring and autumn migrations, before (2–4 years) and after (1–4 years) signs were installed. Night-time vehicle speeds were monitored in 2000–2001.

    (Summarised by: Rebecca K. Smith)

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