Help Forum

Help requested posted on 4th June 2013:

20 mphs

We are currently investigating benefits of 20mph in residential streets. I am interested in hearing from any local authorities that have implemented 20mph zones/limits in all residential streets and from any authorities that have currently dismissed the idea.

Clair George
Peterborough City Council

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Response posted on 4th June 2013 by:
Mark Tune
Warrington Borough Council
T: 01925442695

20mph speed limits

Hello Claire,

We are currently prparing the second year of a 3 year implemnetation programme for 20mph speed limits in the majority of residential streets. The consil's commitment ro 20mph was made after considering the results of 18 month pilots to atempt to study the potential benefits. There are reports detailing the pilot studies plus the framework for implemnentation on our website at got to the downloads section at the bottom of the page for the links to the reports.

I hope this helps


Mark Tune
Traffic Management & Road Safety Manager

Response posted on 4th June 2013 by:
Kate Carpenter
T: 07920 143940

20 limits or 20 zones

Hi Clair, there's loads of evidence online, inc the new Road Safety Observatory: this link is page 2 of ebvidence list for 'speed' section and includes 20 limits and zones: It's not easy to find a 'what's the entire evidence in one place' but this is a good start.

20 limits (signs only) have in many places been of no benefit or worse - a report in LTT on Cambridge 20mph limits said that in quite a few of the scheme sites, speed went UP when the limit was reduced from 30 to 20 (presumably drivers seeing 30 as reasonable, 20 as absurd). 20-campaigns have lead to a rapidly developing polucy throughout London (even ring road routes being 20 in islington for example) and other places (Brighton etc). Area-wide policy for all local roads to be default 20mph is largely untried (some evidence eg Hull I recall) showed signs-only had almost no effect - but with so much of the network changing it could prove interesting.

If people feel roads are then safe, and they walk and cycle in great enough numbers, the road safety benefits (safety in numbers) may outweigh any risk of 'misleading 20'. More important is the public health angle: if 100 people take up cycling because you do loads of 20s and they feel safe, the financial reward in public health terms is vast, which is why health bodies are paying for masses of 20mph in NW England - see if your Director of Public Health can help with some joined up policy? See World Health site: where you can quantify the financial results of more walking and cycling in your 20 schemes.

My start point would be (for 20 limits):
1. Are speeds already appropriate (low 20s range)? If yes, 20 limit is OK (but probably no benefit)
2. Are speeds higher than 30? If yes, you'll almost certainly need some engineering to get speeds into range
3. Toughest case: are speeds high 20s? If yes, you'll probably get max 1 or 2mph reduction and this might not be enough. Some places are using Commnity SpeedWatch in these places to get a bit of extra behaviour change (but not 24 hour!)

For 20mph zones, I'd encourage the new public realm design approach (see and Manual for Streets II) rather than humps and chicanes (all a bit 1980s-90s (myself to blame too). Sustrans have some really good low-cost ideas for street changes and community-delivery too.

Hope that helps. Kate :)

Response posted on 5th June 2013 by:
Haydn Vernals
Any other organisation
T: 01133916883

20mph Limits

Hi Clair

I did a lot of wotk on limits whilst I worked for Calderdale 08-12, where there wasn't a great casualty record to justify stronger measures, developed a simiple casualty rate spreadsheet for the entire built up areas of the borough, gave weightings to various user types and for more recent casualties, whiched helped prioritise a programme - as soon as you start, everyone will want the treatement, so you need to protect your corner and have a strong evidence case for which areas you treat first. Results didn't yeild a great drop in speeds, generally 1-2mph, but did yeild a good drop in casualty rates.

Drop me a line if you want to ask anything specific



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