Public Health Research Shows a 20mph Default Speed Limit Could Save £58-£94M in Wales

“Road traffic injuries, air pollution and obesity are an inter-related, interdependent triad. The challenge facing public health is identifying robust interventions with positive effects on all three”[1].  Public Health Wales researchers have quantified the benefits of default 20 mph limits and say it is “the solution”1 to increasing public health problems.

[1] Reproduced from The Journal of Epidemiology & Community Health, Twenty miles per hour speed limits: a sustainable solution to public health problems in Wales, Sarah J Jones, Huw Brunt, Mar 23, 2017, with permission from BMJ Publishing Group Ltd

Dr Sarah J Jones, Consultant in Environmental Health Protection and Injuries Lead for Public Health Wales has published a paper with Huw Brunt, Consultant in Environmental Public Health Protection - ‘Twenty miles per hour speed limits: a sustainable solution to public health problems in Wales’, in the Journal of Epidemiology and Community Health, March 20171.  Researchers state “if all current 30 mph limit roads in Wales became 20 mph limits, it is estimated that 6–10 lives would be saved and 1200–2000 casualties avoided each year, at a value of prevention of £58M–£94M1”.  With better air quality from a default 20mph, overall pollution related deaths decrease and many hundreds of life years are saved.  The evidence review suggests benefits in terms of road traffic casualties, air quality, active travel, noise pollution, greater social inclusion, greater community cohesion and local business viability. 


Anna Semlyen, 20’s Plenty for Us Campaign Manager, MSc Health Economics said

“20mph limits improve public health.  Medical science and health economics proves a default 20mph limit dominates with conclusive benefits clinically and financially versus the do-nothing option of retaining a default 30mph. We must act on the evidence base.”


20’s Plenty for Us estimates a 20mph signed Welsh default would cost £2M outside Cardiff[1] (which has already agreed a 20mph policy). £2M is a tiny cost versus the huge prevention of injuries benefits of £58-£94M annually. Default 20mph limits have a cost benefit ratio of at least 1:29 in first year in casualties avoided alone for about eight times less cost than each authority separately going 20mph under localism.


Public Health evidence favouring a 20mph default is conclusive. 20’s Plenty for Us call on the Welsh Government and Public Health Wales to work together to make a default 20mph a reality. It is an affordable, do-able policy. As an interim measure, Welsh Assembly members could delegate powers to allow Local Authorities to sign the edges of communities as 20mph unless otherwise signed.  The same public health arguments follow elsewhere.  Mark Ruskell Green MSP is launching a pre-legislative consultation on default 20mph limits for Scotland this April.

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