Study questions impact of 20mph schemes on public health

11.05 | 7 November 2019 | | 4 comments

A new study has 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 they 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’.



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    Could it be argued, that in 20mph zones, health benefits could be reduced, as there will be the likelihood of more vehicles per mile, assuming correct vehicular spacing, at 20mph than at 30mph and the airflow which will disseminate vehicle fumes, will be less at 20mph than at 30mph?

    Derek C Donald, Inverness
    Agree (12) | Disagree (5)

    I find that it is not so much the 20 mph limit that irritates me, but the speedbumps. I can see a need for speed restrictions in school areas, because children generally lack an ability to judge speed and may be distracted by their phones and/or friends.

    Speedbumps which conspire to ruin your back and your car (no matter how slowly you go) seem to have been installed purely to make driving unpleasant.

    Agree (4) | Disagree (10)

    Academics and consultants of any persuasion can usually be relied upon to confirm that more studies are needed.

    But it is interesting that this report and conclusion has been done by public health academics.

    Pat, Wales
    Agree (12) | Disagree (3)

    “New study” alert! Conclusion?… ‘more rigorous evaluations are required in order to draw robust conclusions’. So, another ‘new study’ is necessary.

    Hugh Jones
    Agree (15) | Disagree (1)

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