Busting the 20mph Limit Myths

Here we "bust" all the 20mph myths that opponents so often use as an argument against implementing an appropriate limit for residential, urban and village streets



20mph vs 30mph journey time

20mph (esp side roads) doesn’t significantly alter trip times or inconvenience drivers.  Jams & stops do.  Constant 30mph is rare due to bends, junctions etc. Going fast between obstructions = extra wait at next stop. https://www.youtube.com/watch?v=ZECXj_qQGL4&feature=youtu.be https://www.youtube.com/watch?v=pW_fyuybDYw&noredirect=1


20mph is OK near schools in term time at drop off & pick up times only

80% of child casualties happen on non-school trips. Families need wide area limits for child protection from road injury – their top risk.  Older people are even more likely to die or be seriously injured – 20mph is 10 times safer (than 30mph) for 60+yr olds compared to 7x for others  http://www.20splentyforuk.org.uk/BriefingSheets/How_school_safety_zones_are_not_a_priority.pdf http://www.20splentyforuk.org.uk/BriefingSheets/older_people_deserve_20mph.pdf  http://www.20splentyforuk.org.uk/BriefingSheets/Wide_20mph_Limits_Help_Children_and_Families.pdf

Variable limits only eg not at night

Variable limit digital signs are costly & can’t go on a wide network. So limits end up inconsistent, confusing & don’t reduce fear of speed or increase active travel significantly.

Casualties fall, but what about Killed & Serious Injuries KSI?

Detractors cherry pick data, pointing to raised KSIs in some places - by tiny, insignificant amounts.  KSIs are rare events.  Small datasets are unreliable.  In most 20mph places KSI fall along with total casualties.

Numbers of injuries on 20mph roads

The number & length of 20mph roads is rising (& 30mph roads falling).  Absolute numbers of injuries on 20mph roads could rise, whilst casualties per km fall. Denominator matters!

Income generation from fines –

Compliance is by engagement, pacer vehicles, speed watch volunteers, warning letters, speed awareness courses, occasional enforcement days with a few Fixed Penalty Notices & very rare points or prosecutions http://www.20splentyforuk.org.uk/Press_Releases/Police_Toughen_20mph_Limit_Enforcement_Guidance.pdf

Drivers could lose their licences

Police are not using 20mph limits to add points to licences or remove driving rights http://www.20splentyforuk.org.uk/Press_Releases/Police_Toughen_20mph_Limit_Enforcement_Guidance.pdf

Speedometer watching distracting

Drivers must check their speed whatever the limit. Speedometer checking should happen at 20 & 30 & 40mph, especially in urban areas. Highway Code

On 20mph roads people might take more risks

20mph is 7-10 times safer than 30mph. It is unlikely that people become 7-10 times more careless where 20mph limits are signed.  Massive risk compensation is an unproven fallacy


Drivers don’t obey 30mph & won’t obey 20mph

Average & faster road speeds decrease eg in Portsmouth by 6-7 mph slower on previously 25mph+ roads. Even 1mph matters. Every 1mph less reduces casualties & severities by 6%


Educate pedestrians

Yes educate. Yet studies show road safety education alone hasn’t reduced casualties. Slower speeds works & is recommended by WHO. Don’t blame the victims! http://www.20splentyforuk.org.uk/BriefingSheets/Dont_blame_pedestrians.pdf

20mph & efficiency

Modern vehicles are efficient at 20mph. A lower gear isn’t always needed.  Fuel use and pollution fall due to smoother driving. http://www.20splentyforus.org.uk/BriefingSheets/pollutionbriefing.pdf

Popularity effects

Drivers want 20mph & support rises post implementation. It’s a vote winner! http://www.20splentyforus.org.uk/BriefingSheets/20mph_Support_Rises_Briefing.pdf

Nanny state

Drivers cannot self select the limit.  All UK roads have a limit  Highway Code

UK has safe roads

Not if you are a pedestrian or cyclist, where the UK is very high risk on international comparisons. Pedestrians are 24% of fatalities

Business effects

Businesses pick up the bill now for road danger & injuries. Profits  & tourism rise with slower speeds as footfall rise http://www.20splentyforuk.org.uk/BriefingSheets/Businesses%20Profit%20from%2020mph%20limits.pdf



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  • Rod King
    commented 2022-04-12 13:54:36 +0100
    Its not up to me Gary. Its the elected representatives in London who decide on speed limits in London. Thank you for your comment.
  • Gary Dorrington
    commented 2022-04-12 13:51:47 +0100
    Half of this stuff is rubbish the introduction one 20 mph on the embankment has caused so much more pollution that the mayor has asked for drivers to turn their engines off when stationary, in fact the introduction of cycle lanes across London has Brough pollution levels dangerously high it has had an adverse effect ,on residential streets the 20 mph is acceptable but on other roads Its just being used to fine motorist and coin money from them, I don’t and never will accept or agree with Rod Kings campaigned for 20 is plenty as this has now got out of control and I was never consulted for an opinion, even at night these are still in force and yet electric scooters and bicycles are overtaking cars and not being prosecuted, my over all opinion is to leave well alone and one mans view is not that of another especially when he doesn’t even live in London yet wants to set the speed limit