Safeguarding the health and wellbeing of future generations by introducing Wales-wide 20mph speed limits Sarah J Jones, Huw Brunt
Evidence summary -Effect of 20mph on health and wellbeing
Adopting 20mph as the default speed limit for Wales can deliver on the goals of the Well-being of Future Generations Act (WFGA). The potential health gain is significant. To assess its effectiveness as a public health intervention, we reviewed the evidence in the context of the act and modelled likely outcomes with
specific regard to injury prevention and air pollution.
Estimated effect on road traffic casualties Estimated effect on air pollution related ill health
A Wales-wide 20mph speed limit has the potential to have significant positive effects on health and deliver on all seven goals of the WFGA. We have estimated some health effects, but it is likely that there will be more, cumulative positives that are greater than individual effects but these are more difficult to measure. The road casualty savings alone make the case for change.
Road traffic casualties
Decreases in injuries, crashes, pedestrian and child pedestrian injuries of 17 to 70%
Air pollution 12% reduction in gear changes, 14% in braking and 12% in fuel use; transport emissions reduced in residential areas by 12%
32% reduction in NOx when average speeds drop from 31 to 19mph
48% reduction in NOx emissions with a calmer driving style
Acceleration accounts for 35-55% of pollutants
Decrease in NOx emissions of 24-31%
Active travel 12-25% increase in walking and cycling (Bristol)
Three fold increase in cycling to schools (Edinburgh)
Noise 2dB reduction in traffic noise
Inequalities Narrowed, differences across areas equalised
Social inclusion Improved and enhanced
Increased, communities improved
Local business viability
Improved; people using active travel to visit shops spend more money
Annual average in 30mph limits
Estimated annual average at 20mph
Savings Casualties 1988
Deaths YLL Costs (M)
Current 231 2768 121.70
20mph 293 3521 154.80
Change 63 753 33.1 Fine particulate matter
Current 386 4629 203.50
20mph 269 3230 142.00
Change 117 1400 61.5
Better traffic flow, including public transport and commercial vehicles More walking & cycling due to fewer crashes Local economies more viable & resilient
And better air quality, enhancing the natural environment & supporting ecological resilience.
And better cardio-respiratory health due to better air quality Better general health through less obesity & more physical activity due to more active travel & outdoor play Better mental health linked to all of above.
And reduced inequalities; more deprived areas have greater ranges of traffic speeds & vehicle types.
And greater social cohesion & connectedness.
And more walking, cycling & outdoor play.
And more active travel, less fossil fuel use and fewer impacts of climate change.