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Effects of city-wide 20 mph (30km/hour) speed limits on road injuries in Bristol, UK

Bornioli, Anna; Bray, Isabelle; Pilkington, Paul; Parkin, John


Issy Bray
Associate Head of Department, Research and Knowledge Exchange

John Parkin
Professor in Transport Engineering


Twenty miles per hour (32 km/hour) or 30 km/hour speed limits represent a potential strategy to reduce urban road injuries and are becoming increasingly widespread. However, no study has conducted a robust evaluation of the effects of city-wide 20 mph speed limits on road injuries. This study reports the effects of such an intervention, based on a natural experiment that took place in Bristol, UK. Based on a stepped-wedge design using count data, negative binomial regressions showed that between 2008 and 2016, the 20 mph speed limit intervention was associated with a city-level reduction of fatal injuries of around 63% (95% CI 2% to 86%), controlling for trends over time and areas. There was also a general trend of reduction of the total number of injuries at city level and in 20 mph roads. These findings highlight the potential benefits of city-wide 20 mph speed limits. We hypothesise that this city-wide approach may encourage a general behaviour change in drivers that, in turn, may contribute to reducing injuries across the city.

Journal Article Type Article
Publication Date Feb 1, 2020
Journal Injury Prevention
Print ISSN 1353-8047
Electronic ISSN 1475-5785
Publisher BMJ Publishing Group
Peer Reviewed Peer Reviewed
Volume 26
Issue 1
Pages 85-88
APA6 Citation Bornioli, A., Bray, I., Pilkington, P., & Parkin, J. (2020). Effects of city-wide 20 mph (30km/hour) speed limits on road injuries in Bristol, UK. Injury Prevention, 26(1), 85-88.
Keywords speed, planning, public health, motor vehicle, longitudinal methodology
Additional Information This article has been accepted for publication in Injury Prevention, 2019 following peer review, and the Version of Record can be accessed online at:


Effects of city-wide 20 mph (30km/hour) speed limits on road injuries in Bristol, UK (239 Kb)


Copyright Statement
© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

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