20mph Myth Buster

There are many misleading myths around 20mph speed limits. Here are some common myths and the true facts. If you have other questions please get in contact.

Myth: 20mph is only needed around school gates

Truth: If you agree with 20mph around school gates, consider that children do not appear 100m away – they walk, scoot or cycle from home, up to a mile away. Children need slower speeds throughout the journey to school.

Myth: We only need it at school times, it's silly to drive at other times at 20mph

Truth: 80% of child casualties happen on non-school trips,1 so driving slower all the time is necessary to reduce accidents and make your street an enjoyable environment for everyone.

Families need wide area limits for child protection from road injury – their top risk. Children don’t just go out at school times, they also go to parks, shops, cafes (just like the rest of us) at weekends and evenings, so just having 20mph limits at just school times does not give them the protection they deserve.

Additionally, it is not just children that benefit from slower speeds on the road. Older people are even more likely to die or be seriously injured – 20mph is 10 times safer (than 30mph) for 60+yr olds1.  Nearly half of all pedestrians killed are aged over 60.1

Myth: Car journeys take longer

Truth: 20mph on residential roads doesn’t significantly alter trip times or inconvenience drivers, as constant 30mph is rare in built up areas due to junctions. Often going at 30mph just means an extra wait at the next traffic lights. Try it for yourself by going up Surbiton Hill Road at 20mph!

Myth: The police won’t enforce

Truth: The MET and our safer neighbourhood teams already conduct speed checks on current 20mph zones in Surbiton.2

Myth: It’s a waste of money

Truth: Sign only 20mph speed limits reduce accidents so actually save the public purse. The average cost to the public purse of a road traffic casualty is £47,740. 8Any reduction is not only better for those involved, but also a cost saving to the taxpayer.  A saving just a couple of accidents, will pay for this scheme and evidence from other UK towns and cities suggest that the number of accidents prevented will be much higher.

Myth: driving at 20mph increases pollution

Truth: A 20mph limit reduces pollution by causing vehicles to travel at a more consistent speed, and acceleration is the main cause of pollution and carbon emmissions.3 Also where widespread 20mph limits have been introduced, walking and cycling has increased.

Myth: It doesn’t increase walking or cycling or make our streets better

Truth: Fear of fast traffic is a significant factor in people’s decisions to walk or cycle. A Brake and Churchill survey found nine in ten UK parents (90%) say fast traffic poses a danger to families and children in their community, and three in four (74%) say their family would walk more if the safety of nearby roads was improved. 4

20mph limits are a way to help people to be healthier and happier, walking and cycling levels rose by up to 12% in Bristol after a 20mph limit was introduced.5

Research has also found that 20mph limits boost the economic sustainability of local areas, as safer areas for walking and cycling are seen as more desirable areas to live, boosting local businesses and increasing the value of homes in these areas.6

Myth: As accidents are already low in Kingston, so it won’t help

Truth: It is true that serious accidents are already low in Kingston, especially in residential roads. However, a trial of 20mph limits in Warrington, Cheshire, found pedestrian and cyclist casualties dropped 36%.7 When Portsmouth introduced a wide area 20mph limit, they saw a drop of 18.8% (taking 3 years ‘before’ and 3 years ‘after’). 

Additionally, most pedestrians and cyclists have experienced near misses, which are rarely reported, so accident statistics do not give the full picture. The worry of a potential accident is always in parents’ minds and this affects the amount of walking and cycling they do with their children.

Myth: Parents just need to teach their children road safety

Truth: Of course learning road safety skills is vital for everyone.  However, research has found that children cannot judge the speed of approaching vehicles travelling faster than 20mph, so may believe it is safe to cross when it is not.9

Regardless of whose fault, no driver wants to be responsible for hitting and injuring a child (or any pedestrian), and travelling at a lower speed decreases the likelihood of this happening. If a child runs into the road three car lengths ahead, a driver travelling at 30mph (48km/h) will not be able to stop in time, and will still be travelling at 28mph (45km/h) when they hit the child. A driver travelling at 20mph should just be able to stop in time. 10

Myth: Drivers won’t go slower

Truth: Sign only 20mph speed limits elsewhere have reduced average speeds by around 1-2mph. Evidence from Portsmouth shows that the greater the average speed before the 20mph speed limit was introduced the greater the reduction in average speeds. So for roads with an average speeds of 24 mph or more before the scheme was introduced, the average speed reduction was 6.3 mph, whilst the average reduction over all the roads was 1.3 mph.11

Myth: Government doesn’t support 20mph

Truth: The Department of Transport guidance encourages 20mph speed limits. Circular 01/2013 says “Traffic authorities are asked to keep their speed limits under review with changing circumstances, and to consider the introduction of more 20 mph limits and zones, over time, in urban areas and built-up village streets that are primarily residential, to ensure greater safety for pedestrians and cyclists.”12

Myth: There are no accidents in Surbiton Town Centre

Truth: This is a map of injury causing collisions from 2007 - 201513

Surbiton 20mph map


  1. http://www.20splenty.org/busting_the_20mph_limit_myths and http://www.rospa.com/rospaweb/docs/advice-services/road-safety/drivers/vulnerable-roadusers.pdf
  2. https://twitter.com/MPSSurbiton 13th August 2016 and 19th July 2016
  3. Car pollution, Environment Protection UK, 2013
  4. http://www.brake.org.uk/info-and-resources/facts-advice-research/road-safety-facts/15-facts-a-resources/facts/1256-speed-communities
  5. Greater Bristol Cycling City, Bristol City Council, 2011
  6. Motor Vehicle Speeds: Recommendations for Urban Sustainability, Transportation Research Board, 2012
  7. 20mph Speed Limit Pilots Evaluation Report, Warrington Borough Council, 2010 
  8. http://www.rospa.com/road-safety/advice/roads/engineering/
  9. Reduced Sensitivity to Visual Looming Inflates the Risk Posed by Speeding Vehicles When Children Try to Cross the Road, University of London, 2011
  10. http://www.brake.org.uk/info-and-resources/facts-advice-research/road-safety-facts/15-facts-a-resources/facts/1255-speed
  11. http://www.cyclinguk.org/sites/default/files/speed-limits-portsmouth.pdf
  12. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/63975/circular-01-2013.pdf
  13. http://road-injuries.info/map.html
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