Wide 20mph Limits are Effective

Lower speeds improve streets.  20mph raises safety and quality of life.   Signed 20mph limits are proven effective.  Maximising compliance is key.  Behaviour change is through engagement and light enforcement.

This 2-page briefing sets out the wide evidence that 20mph limits are beneficial to communities.

UK wide-area or ‘Total 20’ schemes sign between 70-94% of residential roads at 20mph. Traffic engineering humps are not needed.  Safety improves.  Advantages also include increased active and independent travel, better public health, greater access for all, equality gains, that local shops prosper, reduced fuel use plus 20mph’s rising popularity. 


Safer:  In Portsmouth speeds reduced 0-7mph with an average of 1.3mph.  Some roads were already low speed. Where it matters, on roads with before speeds over 20mph, safety improved. There were 22% fewer casualties[1].  York found 3mph reductions in pilots[2].  Graz in Austria adopted a 30-km/h (20mph) limit throughout most of the city in 1992. It reduced serious casualties by over 25% as well as significantly reducing noise and air pollution[3].The laws of physics mean collisions are fewer as there is more time and space for everyone to react and take avoiding action. If hit at 20mph it hurts a lot less than at 30mph. Pedestrians are seven times more likely to survive at 20mph. 

  • The World Health Organisation backs Total 20 as proven for pedestrian safety.  WHO says “Implement area-wide lower speed limit programmes, for example, 30 km/h” (20mph)[4].
  • The EU strongly recommends 30km/h (20mph) for urban and residential areas.
  • Limits cost 47 times less and are 7 times more cost effective per mph reduced than humped zones[5].
  • Health experts including NICE, Duncan Selbie Chief Executive of Public Health England, the North West Health Observatory and Prof Danny Dorling all advocate Total 20 where people live. 


Cost effective: Total 20 is affordable at £3 per head[6].  With a road death valued at £1.689m and a serious casualty at £189k[7] a Total 20 policy must only prevent one death or 3 serious casualties to pay back its one off implementation cost for a 190,000 population.  Warrington had first year rates of return of 800% on casualty prevention[8].  Active travel increases. Bristol found 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 and that cyclist casualty numbers fell by around 40%[9].  Savings from the health economic gains from increased activity outweigh those of casualty avoidance alone by ratio of 1.6:1[10], even before disability benefits and obesity changes to the next least unfit cohort of people who begin exercising more.

Further success measures also include that:


  • Every UK local authority that has trialled a wide-area 20mph signed scheme has decided to roll it out even wider – e.g. across York, Lancashire, Warrington and Bristol.
  • Department for Transport guidance increasingly requires traffic authorities to consider 20mph limits where there is, or could be, demand by vulnerable road users e.g. children, elderly, walkers or cyclists. 
  • The Department for Transport are reviewing guidance on repeater signs.
  • Scrutiny committees (cross party panels of Councillors) in Warrington, Greenwich, Brighton, Manchester, Richmond, Gloucester, Darlington and Hartlepool all support Total 20 as a best value.
  • Islington has made arterial routes 20mph following the success of residential 20mph.  Camden and Southwark plan to include main roads at 20mph too.
  • Popularity rises after implementation - “Residents’ support for a maximum speed limit of 20 mph or less on all residential streets rose from 67% to 83%” in Bristol[11].  In Graz less than 50% of residents supported the initiative at the time but, after benefits became evident, support grew to 80%.
  • Businesses profit from 20mph limits raising footfall[12].
  • Drivers use less fuel worth up to 16p per litre based on German evidence of using 12% less fuel[13].
  • Pollution falls or is unaffected13. 20mph limits are good for the environment[14].
  • Quieter streets matter. 55% of those living in urban areas with over 250,000 people endure daily road noise levels above the lower EU benchmark for excess exposure[15].  In urban areas with speeds of between 20 and 35 mph, reducing speeds by 6 mph would cut noise levels by up to 40%[16].
  • Heritage and tourist places and those with high educational levels have been leaders in choosing Total 20 e.g. Oxford, Cambridge and York. 20mph is the smart way to help tourism, their economy and reduce some of the negatives of car traffic.
  • Transport for London have accepted that some City Hubs on the capital’s red routes, like the IMAX roundabout by Waterloo bridge need to be limited to 20mph to balance movement and liveability.


The majority of transport experts think wide 20mph is inevitable. The question is no longer ‘Why 20mph?’ but ‘Why not 20mph?’ Over 11m people’s authorities agree to Total 20mph.  


A 30mph limit doesn’t offer any advantages over 20mph. Islington found that changing to 20mph didn’t change journey times (due to stop/go traffic).  Bristol showed bus times were unaffected. The majority of drivers willingly comply once they understand 20’s plenty.  Yet, education and social media must sell the message.  When a 20mph limit is establishment endorsed with signs, the decent majority of obedient drivers slow those behind. Speed becomes socially unacceptable. Occasional police enforcement with monitoring and fixed penalty notices are all that’s required (i.e. no additional police resources).   


Wide area 20mph limits work and are affordable.  We should all demand Total 20 of our Councillors. It’s up to us to ask. People must demonstrate support to politicians so that they have a mandate for change.

[1] Portsmouth 22%.  8% better than the national downward casualty trend - http://assets.dft.gov.uk/publications/speed-limits-portsmouth/speed-limits-portsmouth.pdf

[3] Speed Kills: The Complex Links Between Transport, Lack of Time and Urban Health, Paul Joseph Tranter http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2845829/

[6] York budget £600k for 200k population is £3 p/head, Oxford £2, Portsmouth £2.75, BathNES £3.58

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

[10] http://www.ucl.ac.uk/news/pdf/transportactivityhealth.pdf Transport’s non casualty costs (excluding disability benefits):-Direct NHS £1.08bn, Indirect NHS £8.2bn, Other Costs from National Audit Office £7bn=£16bn vs £10bn casualty costs pa.

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