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Providing evidence to improve practice

Action: Reduce legal speed limit Terrestrial Mammal Conservation

Key messages

Read our guidance on Key messages before continuing

  • One study evaluated the effects on mammals of reducing the legal speed limit. This study was in Canada.




Supporting evidence from individual studies


A controlled, before-and-after study in 1983–1998 along a highway in Alberta, Canada (Bertwistle 1999) found that speed limit reductions and enforcement did not reduce vehicle collisions with bighorn sheep Ovis canadensis or elk Cervus canadensis. Sheep collision rates were similar in the reduced speed zones after limits were reduced (10.4 collisions/year) compared to before (10.3/year). Concurrently, in control areas where the speed limit was not reduced, there were fewer collisions in this second period (2.5 collisions/year) than the first period (3.4/year). Elk collisions increased with the speed limit reduction (after: 9.6/year; before: 7.8/year) but increased by more in the control zone (after: 14.3/year; before: 7.8/year). The local elk population increased 178% during the study. In 1991, the speed limit along a rural two-lane highway was reduced from 90 km/h to 70 km/h on three road sections (2.5, 4.0 and 9.0 km long). Monitoring in 1995 indicated that <20% of vehicles obeyed the 70 km/h limit. On average, 5,475 speeding tickets were issued/year. Animal-vehicle collisions were monitored for eight years before and eight years after speed limits were reduced, on three 2–3-km-long road sections for sheep and one 30-km-long section for elk. Vehicle speeds were monitored along two road sections in 1995.

Referenced papers

Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.