Public Health Gains from 20mph Limits

Public Health England’s Chief Exec Designate, Duncan Selbie, has used 20mph limits as an example for Public Health Directors of how they can provide visible, accessible and practical evidence to local authorities to benefit community health and “reduce child accidents and deaths by an important margin” . Liverpool and Bristol’s PCT’s have given funding or expertise towards implementing community wide 20mph limits. Health improves and people are better protected in 20mph areas.

With Public Health moving to Local Authorities, transport policy is increasingly recognised as affecting well being.  The National Heart Foundation, Association of Directors of Public Health[1] and many Joint Strategic Needs Assessments support community wide 20mph limits for built up areas. Over 8 million people’s authorities have agreed residential 20mph limits e.g. York, Lancashire and Cambridge. Humps are not needed and slower top speeds do not affect trip times.  20mph health gains include:

Safer for all, especially kids and the less mobile

All are more able to notice hazards and stop to avoid a crash. Primary age children can only reliably judge traffic speeds up to 20mph[2]. Cars are the biggest killer of children and young adults in Britain. NICE recommend 20mph to protect kids[3].  Up to 140 fewer children p.a. would be killed or seriously injured in the North West with 20mph zones[4]. There are 22% fewer casualties[5]. Injuries are less serious or disabling. Road fear reduces. Children need less escorting. Some car trips switch to other modes. Less traffic further reduces road danger.

Physical Health

People’s fitness improves with slower speeds. Health improves with cleaner air and through more active travel exercise, increased walking, cycling and public transport.  Children play out more.  There is a positive spiral.

Activity Saves Money

Bristol found of its 20mph limits, using a mean of a 23% increase in walking and a 20.5% increase in cycling that, for each £1 spent, the return on investment for walking is £24.72 and cycling is £7.47[6]. Active lifestyles help reduce obesity and heart disease, saving the NHS money.  Warrington reported a 800% rate of return on investment in its 20mph pilots on casualties avoided[7].


Health inequalities between rich and poor narrow.  Poorer boys especially benefit from raised life expectancy[8].


When 30km/h (18.6 mph) zones were implemented Germany, drivers changed gear 12% less often, braked 14% less and needed 12% less fuel[9], reducing air pollution, asthma and other respiratory diseases.


Compared to 30mph, 20mph means 3 decibels less traffic noise. People can more easily listen to each other and we all sleep better. In urban areas with speeds up to 35mph a 6mph reduction cuts noise by up to 40%[10].


Those whose roads are not dominated by traffic have more local friends and known neighbours[11]. Children have more playmates. Neighbourliness brings a culture of exchange, ‘looking out for each other’ and favours that further enhance quality of life through a stronger community.  Loneliness reduces.

Mental Health

There is less road rage when people drive respectfully. Increasing everyday exercise improves mental health. Less fear, loneliness, noise or disturbed sleep all add mental health gains. 


The elderly, families with small children and those with mobility issues or without cars are more able to cross roads, reducing isolation.  20mph improves access to work, education and leisure opportunities to all.  

Place not Empty Space

A sense of ‘place’ rather than just an empty space results when drivers slow down. Streets are no longer just thoroughfares, but a quality environment to savour, meet and even play.

In Liverpool the PCT is contributing 40% - £665k of £1.665m – to 20 mph limits. £400k (28.5%) of £1.4m to implement 20mph signed limits over four years, plus £265k for perception surveys and extensive public health promotion of “The 20 Effect” for safer streets.  Leading Directors of Public Health are actively saving lives and preventing illness with 20mph limits.  Is yours?

[2] John P. Wann et al, in Psychological Science OnlineFirst, March 9, 2011

[3] NICE. Preventing unintentional injuries among under-15s

[4] North West Public Health Observatory  Modelling of humped zone casualty reductions, not signed only limits

[5] Interim Evaluation of 20mph Speed Limits in Portsmouth. Atkins 2010

[7] Warrington Borough Council – 20mph Speed Limit Pilots Evaluation Report – Para 13.10

[8] Prof Danny Dorling, Roads, Casualties and Public Health. The Open Sewers of the 21st Century. PACTS Westminster Lecture 23 Nov 2010

[9] An Illustrated Guide to Traffic Calming.  Dr Carmen Hass-Klau 1990 

[10] Campaign for Better Transport for the UK Noise Association 2009 

[11] Donald Appleyard Liveable Streets 1981  

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