Go slow: an umbrella review of the effects of 20 mph zones and limits on health and health inequalities.

BACKGROUND Transport is an important determinant of health and there is a well-established association between socio-economic status (SES) and risk of road accidents. Effective traffic calming interventions such as 20 mph zones and limits may therefore improve health and reduce health inequalities. METHODS Systematic review methodology was used to identify systematic reviews of the effects of 20 mph zones (including speed limits and road humps) and 20 mph limits on health and SES inequalities in health amongst adults and children. RESULTS Five systematic reviews were included. Overall, they provide convincing evidence that these measures are effective in reducing accidents and injuries, traffic speed and volume, as well as improving perceptions of safety in two of the studies. There was also evidence that such interventions are potentially cost-effective. There was no evidence of the effects on SES inequalities in these outcomes. CONCLUSION Twenty mile per hour zones and limits are effective means of improving public health via reduced accidents and injuries. Whilst there was no direct evidence on the effects of interventions on health inequalities, targeting such interventions in deprived areas may be beneficial. Further controlled evaluations that specifically examine SES effects are required.