Research & reports

Title: Report into the effectiveness of 20 miles per hour (mph) road speed limits

Organisation: Department for Transport
Date uploaded: 4th December 2018
Date published/launched: November 2018

This research has been carried out by Atkins, Aecom and professor Mike Maher (UCL), who were commissioned by the DfT in 2014 to address a gap in the evidence available on the effectiveness of 20mph speed limit (signed only) schemes.

12 case study schemes were studied, from a variety of area types, road types and scale.

There are two reports a 68-page headline report and a 221 page technical report.

Headline findings include:

20mph limits are supported by the majority of residents and drivers
There has been a small reduction (less than 1mph) in average (median) speed
Vehicles travelling at higher speeds before the introduction of the 20mph limit have reduced their speed more than those already travelling at lower speeds

The reports say there is not enough evidence to conclude that there has been a significant change in collisions and casualties following the introduction of 20mph limits in residential areas.

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