Published July 13, 2019, positive outcomes of the city-wide speed limit reduction in Bristol, UK: https://injuryprevention.bmj.com/content/early/2019/07/25/injuryprev-2019-04...

Amazingly, these positive changes "did not involve the introduction of any physical traffic calming measures" ( https://travelwest.info/project/ee-no-185-the-effectiveness-of-a-20mph-speed... ).

That being said, *roadway design is still understood to be the most effective way to reduce speeds*; this study just suggests that the posted limit alone can have a significant impact, and that the general behaviour change from a city-wide shift is greater than reducing limits in only designated areas.

Key takeaways:

- After implementing 20mph default speeds, *speeds decreased city-wide, even on streets whose limits were unaffected: "**This suggests that city-wide 20 mph speed limits could be an effective strategy for reducing injuries, as it encourages safer driving behaviour that is not restricted to 20 mph roads. * - In support of a city-wide change vs. traffic-calmed zones: *"Interestingly, the reductions in fatalities in Bristol are larger than the 46% reduction in London associated with the introduction of traffic-calmed 20 mph zones,...Therefore, this finding goes some way to supporting city-wide 20 mph speed limits as an intervention to reduce road injuries*."; *The policy recommendation that would follow from this is to implement city-wide 20 mph limits, rather than 20 mph limits in restricted areas of a city* *.*"

*Sean Carlson* (he/him/his)

Active and Safe Routes to School Program, Green Action Centre http://www.greenactioncentre.ca/

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