Scotland’s aspiration for more liveable communities via 20mph limits is ideally timed to benefit from new speed limited vehicles

Recent changes to vehicle specifications applicable from 2022 have ramped up expected returns and effectiveness from the Safer Streets 20mph Scotland Bill being considered by MSPs. Members of the Scottish Parliament (MSPs) have already heard that a national limit is extremely cost-effective. At £10m for 2 years – (only 0.75% of Government transport funds), it pays back in year one. New speed limiting laws make it even more cost beneficial.

MSPs will soon vote on 20mph as the new Scottish speed limit.   The #Saferstreetsbill calls for a national default of 20mph for U and C class (mostly residential) restricted roads whilst councils retain local decisions on roads to keep at 30mph.  Mark Ruskell’s bill has been through consultations and extensive evidence with the Rural Economy and Connectivity Committee (RECC).

Fast traffic blights many streets.  In contrast, when drivers go at a maximum of 20mph, most people survive collisions.  A pedestrian hit at 30mph is equivalent to falling from a third storey window, whilst 20mph is like a first floor fall. Hit at 20mph most people walk away - at 30mph, victims are carried away. 

The RECC heard evidence that a national 20mph limit is the most cost-effective way to protect communities.  The science on impact survivability alone makes a convincing case for a national change as fairer, simpler and cheaper than signing all but a few built up streets. It aligns with the Department for Transport Atkins 20mph report which showed that other transport safety spending options aren’t better value for money than wide 20mph limits. The Safer Streets Bill’s Financial Memorandum (FM) already says a national 20mph change pays back within a year for eight times less cash than if council’s implement 20mph individually at local level[1].

Yet a game changer has happened.  EU speed limiter laws voted through this March state new cars from 2022 must have over-rideable speed limiters and black box crash recorders[2].  Limiters largely remove arguments about non-compliance to 20mph as it is self-enforced in car.  Once there are limited vehicles, speeds fall further than assumptions in the cost benefit analysis of the Safer Streets Bill’s FM (which conservatively estimated 1.7mph–2.7mph reductions x 5% fewer casualties p/mph = 8%-14% [3] fewer injured).  Edinburgh saw 24% fewer casualties[4] in early results (80% of roads went 20mph/ave speeds fell 1.9mph).  20’s Plenty for Us predict 15-20% fewer casualties with a National 20mph limits is a more reasonable updated assumption as speed limiters will raise compliance.  Some cars already have them and even the first few speed limiters is use regularly will effectively set the highway system pace of traffic behind.

20mph nationally is not costly - £10-12m pa for 2 years and this falls with speed limiters due to less policing for compliance.  For context, £10m is 0.75% of the total Sottish Transport budget of £1,317m.  This small change has a huge impact.  The Bill’s FM said casualties prevented were estimated at 8-14% fewer or 335-587 people pa – worth £20.5m - £36.1m pa in prevention savings. With speed limiters, speeding falls as do costs, whilst the benefits rise. If we assume 15-20% of the casualties prevented on Scottish B, C and U class roads (totals were 4,187 of which 25 fatalities, 554 serious in 2016) then 628-836 fewer casualties pa are predicted with a national 20mph limit. The Glasgow Centre for Population Health estimates 500-750 fewer casualties and significant gains to active travel[5].  Some roads will remain at 30mph (and be better complied with). 20mph’s savings are in the table below.

Revision of Financial Memorandum Table 6.  Value of accidents prevented as per DfT costings:


Injury type

Cost per incident £

Casualties prevented per year (15% /20%)

Savings per year (rounded) £m



3.75 / 5

£5m / £6.7m



83 / 110

£15.4m /£20.4m



541 / 722

£8.7m / £11.6m



628 / 836

£29.1 / £41.7m


Using the 20% fewer casualties estimate, prevention of injury savings are £41.7m for years 1-5 = £208.5m.

Policing costs fall as there will be less speeding for officers and courts to deal with once more in-car limiters self-enforce all speed limits.  Using the FM’s lower estimate of £10m Nationally in years 1 & 2 = £20m.

The 20mph policy cost of £20m pays back £208m in savings.

For every £1 spent the rate of return is over £10 in 5 years - an astoundingly high value for money policy with an over 1000% pay back.

Transport Scotland were quoted as saying “more evidence and further consideration needs to be given to the impact and consequences of a nationwide default 20mph limit, including an assessment of Scotland's road network before the measure proposed in the Bill can be fully supported[6]”. By “further considering” the impending speed limiter changes, we can only see increased benefits from the Bill.

Public health experts say there is extensive evidence that impacts are already well understood and are popular. 20mph is best practice according to the EU, World Health Organisation, OECD, Chest, Heart & Stroke Scotland, Cycling Scotland, Friends of the Earth Scotland, Living Streets Scotland, Poverty Alliance, the Royal College of Paediatrics and Child Health, Transform Scotland and Edinburgh Napier University Transport Research Institute[7]

Rod King MBE, Founder of 20’s Plenty for Us said

“The changes to vehicle specifications with speed limiters and “black boxes” is a complete game-changer with regard to wide-area 20mph limits. MSPs can grasp the opportunity for Scotland to become a world-wide leader by taking notice of changing automotive technology and setting the speed limits on community roads around its aspirations for safety and liveability. It will prevent an estimated 628 – 836 casualties per year.  With a pay back of £10 per £1 spent, Scotland can leapfrog England who are doing it authority by authority. This “English Way” is inconsistent, cumbersome and costly. There is global consensus that 20mph is best practice on for roads where people live, work and play. Children and vulnerable people deserve protection from traffic that maims and kills.  And this is a move that protects drivers as well as pedestrians and cyclists.

We urge MSPs[8] to vote for the Safer Streets 20mph Bill to make Scottish communities even better places to live, work, play, shop and learn. “

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[8] MSP details are at

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