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 report says 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.

The 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.

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

Road Safety News will cover the report in more detail in the next 24 hours once we’ve had time to digest its content, and heard from stakeholders.

Click here to access the report.

Jesse Norman quote
In an open letter to local authorities, Jesse Norman, road safety minister, said: “Overall the introduction of 20mph limits led to a small reduction in median speed (less than 1mph), but vehicles travelling at higher speeds before the change of speed limit reduced their speed more than those already travelling at lower speeds.

“The study found insufficient evidence to conclude that in resi areas the introduction of 20mph limits had led to a significant change in collisions and casualties.

“Overall, there was a small but statistically significant improvement in reported levels of cycling and walking.

“Important benefits of 20 mph schemes include quality of life and community benefits, and encouragement of healthier and more sustainable transport modes such as walking and cycling.”

Stakeholder reaction

Rod King, 20’s Plenty for Us
“We welcome the report. It demonstrates that those authorities setting the context for their future liveable cities and active travel by means of wide-area 20mph limits are achieving similar results in terms of speed and casualty reductions as those spending money on more traditional road safety interventions. But having set that context, the 20mph authorities will be able to build with additional active travel interventions which all build on that context. We note that public and community support for 20mph limits is high.

“The report also showed that police enforcement, or lack of it, was a key driver in compliance levels but the report did not look at how these varied amongst the case studies chosen. Our experience shows us that the key factors in speed reduction and outcomes are whether an implementation is authority-wide, the level of cross party political support, the level of multi-agency support, police enforcement and the level of community consensus change engagement. We would have preferred evaluation comparing these across case studies to understand the relative influence of such factors.

“We also note that the choice and aggregation of speed data may well have blurred the results. GPS speed readings were said to be just 3% of actual vehicle movements and may well be biased due to only being measured on TomTom devices with GPRS feedback or on software update. In addition static sites measurements tend to be at free-flowing positions. Whilst accepting these limitations they do show the difficulty of using such data.

“Some key messages were that the lack of enforcement increases non-compliance and needs to be enhanced. Independent Speed Adaptation on “works vehicles” could also condition this. And both of these work so much better when the correct limit of 20mph (as endorsed by WHO, OECD, ETSC, etc) is set for where vehicles mix with pedestrians and cyclists. In addition a national media engagement that “20 is plenty where people are” would consolidate the developing consensus that the report shows exists.

“In conclusion the report shows that spending money on wide area 20mph limits has no disbenefits compared to other road safety initiatives and sets the context for how we share those public spaces between buildings that we call streets. Its time to step up the roll-out of 20mph limits to a national level so that they can be even more effective and beneficial.”

Credit: RSGB website