RT Journal Article SR Electronic T1 Effects of city-wide 20 mph (30km/hour) speed limits on road injuries in Bristol, UK JF Injury Prevention JO Inj Prev FD BMJ Publishing Group Ltd SP 85 OP 88 DO 10.1136/injuryprev-2019-043305 VO 26 IS 1 A1 Anna Bornioli A1 Isabelle Bray A1 Paul Pilkington A1 John Parkin YR 2020 UL http://injuryprevention.bmj.com/content/26/1/85.abstract AB 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.