Research & reports

Title: Effects of 20 mph interventions on a range of public healthoutcomes: A meta-narrative evidence synthesis

Organisation: Queen's University Belfast (lead organisation on study)
Date uploaded: 19th November 2019
Date published/launched: October 2019

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This study found that while 20mph zones can help improve road safety, there is less robust evidence of any public health benefits.

The study, carried out by 12 public health academics from leading UK universities, set out to investigate the effect of 20mph zones and limits on a range of health outcomes.

The report defines a 20mph zone as a scheme which involves physical traffic calming measures – such as road narrowing or speed bumps – designed to slow vehicles and ensure the limit is adhered to.

In contrast, 20mph limits involve only signage and/or lines to alert drivers to the limit.

The academics evaluated 11 existing studies on 20mph schemes (nine 20mph zones and two 20mph limits), looking at issues including: road traffic collisions and casualties, walking and cycling, changes in mode of transport, air quality, perceptions of road safety and ‘liveability’.

The study concludes that the 20mph zones the researchers looked at were associated with a reduction in the number and severity of collisions and casualties.

However, while the academics suggest that 20mph zones have potential to indirectly impact physical activity and liveability, they found less robust evidence of the effect on air pollution.

In their conclusion, they suggest that while 20 mph zones are effective in reducing collisions and casualties, there is insufficient evidence to draw conclusions on their effect on pollution, inequalities or liveability.

For 20 mph limits, they say more rigorous evaluations are required in order to draw robust conclusions.

For more information contact:
Claire L Cleland (Queen's University Belfast)

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