How the DfT report enables Local Authorities to implement Wide Area 20mph Limits

Jesse Norman MP, the Minister for Transport has written to Councils saying the “WS Atkins report confirms public support for 20mph”.  Many Local Authorities are now reviewing 20mph policies and re-interpreting DfT guidance.

Jesse Norman’s letter[1] on the 20mph Limit Evaluation[2] of 22 November 2018 confirmed public support for 20mph and shows how Local Authorities can implement 20mph schemes successfully.

“Early engagement and buy-in from other stakeholders, including cross-party support from local councillors; clear articulation of the scheme’s rationale, objectives and outcomes; and tailoring of schemes to local circumstances were crucial to [delivering] a scheme to the anticipated quality, programme and cost”.

Mr Noman’s letter emphasises certain aspects of the DfT evaluation:

  1. 20mph is extremely popular: 70%+ support 20mph speed limits.
  2. Benefits of 20mph: quality of life and community benefits; encouraging healthier and sustainable transport modes such as walking and cycling.
  3. Confirms existing guidance (from 2013) on setting local speed limits.
  4. Around 1mph reduction in median speeds and a greater reduction from faster drivers.
  5. Insufficient evidence to draw conclusions about casualty reduction, except Brighton city centre, where casualties reduced significantly. 20’s Plenty for Us notes that casualties have reduced by 20%+ in many places[3] and the dataset used by the DfT could have been anticipated to be too small.
  6. Cycling and walking levels are significantly up in 20mph areas.


Mr Norman’s letter contained some errors and omissions:

  1. Where the letter states that the authors found insufficient evidence, the evaluation actually shows that the case studies areas chosen had insufficient casualties to be able to show whether or not the evidence was statistically significant.  See our critique at
  2. The letter omitted to say that speeds in the area surveyed were already low and the authors acknowledged that lower speeds were not expected.
  3. The letter did not say that the median speed from TomTom data is very suspect – biased by only capturing an estimated 3% of traffic with a disproportionate sample of men, non-local and business users in high end vehicles. Using the median dampens down the effect of slower moving vehicles.
  4. There was no reference to enforcement, when the report confirms non-enforcement as a large factor in low compliance.

The problem

DfT guidance encourages Local Authorities to implement 20mph in residential streets and town/village centres. Councils that interpret the 2013 guidance narrowly often insist on physical calming on faster roads, but then reject the scheme due to the expense.  This means missing the opportunity to agree popular schemes which would lower speeds and danger overall, despite the DfT report showing that speeds reduce most on the faster roads.  Many Local Authorities now include roads in excess of 24mph with limited physical calming for consistency of limit and to cut the number and severity of casualties. Note that Parish and District councils have no statutory responsibility or duty for setting speed limits. That rests with Traffic Authorities. Equally Traffic Authorities do not have the power to devolve that responsibility to lower level elected representatives.

We can choose to make streets better places

From a ‘can do’ mindset of wanting built up area streets to become increasingly vibrant and liveable, the report leads us to these conclusions:

  • A 20mph limit should be the default for urban and village streets with exceptions only where justified.
  • 20mph limits should be subject to robust and routine enforcement.
  • Intelligent Speed Adaptation (ISA) should be mandatory on all works vehicles, such as London Buses.

Possible solutions also include

  • Widening interpretation of DfT guidance to include roads with pre-speeds of 25mph+ with limited physical traffic calming and psychological calming to change mindsets, eg repainting to suggest narrowing and clear marketing of the benefits of 20mph speeds to drivers.
  • Embedding 20mph as the default for residential streets and town/village centres and new developments, in Council Active Travel Strategies and enable bids for sustainable transport funds for 20mph schemes.
  • Lobby for 20mph as a duty of care that all citizens should be able to enjoy; already in place for 25% of the UK population and now being discussed nationally, with cross party support, for Scotland (Safer Streets Bill) and Wales.

Wide-area 20mph schemes are popular AND cost effective - £3-5 per head invested in 20mph pays back in fewer casualties in about six months! It’s a great use of tax payer’s money for a policy with high levels of public support.


[1] Jesse Norman letter reference




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Showing 4 reactions

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  • Andrew Saffrey
    commented 2018-12-13 16:54:36 +0000
    Do you mean by “Using the median dampens down the effect of slower moving vehicles” that the mean speed should be used instead.
  • Rod King
    commented 2018-12-12 15:00:21 +0000
    Actually, compliance isn’t so low. The DfT report says that in 20mph limits most people (70% residential, 85% city) travel at speed less than the enforcement threshold of 25mph. And that using TomTom data which is very biased. But like any speed limit enforcement is a key factor in compliance. So why not make it better.

    And, of course, the whole idea of a speed limit decided by the community is that it sets a community led maximum speed rather than an individual deciding what are “the right places at the relevant times”. And the report shows that wherever 20mph limits are implemented then support increases.
  • Peter Cook
    commented 2018-12-12 12:55:30 +0000
    If “20mph is extremely popular: 70%+ support 20mph speed limits.” then why is compliance with 20mph speed limits so low?
    Originally we were told that 20mph limits would be self enforcing as everyone wanted them, yet now there are many articles on this very site talking about the need for enforcement of 20mph limits / calling for vehicles to be fitted with automatic speed limiting devices.

    Dont get me wrong – in the right places and at relevant times I totally support 20mph zones / limits, but in my opinion they have been vastly overdeployed with a corresponding loss of public support.
  • Rod King
    published this page in Press Releases 2018-12-11 19:23:07 +0000