Lessons to learn from Manchester

In a recent analysis of its 20mph roll-out Manchester City Council have decided to review it plans because pedestrian and cycle casualty reduction in the first Phase implemented in 2012 have not matched the %age reduction in all the roads across the city. They are continuing their roll-out of Phase 2 but may use some of the allocated funding for Phase 3 on alternative road treatments.

Some of the media and 20mph opponents have used this as "proof" that 20mph limits "don't work" and are calling for other cities to "learn from Manchester" and change their 20mph plans.

At 20's Plenty we take the view that all evidence is useful evidence but needs to be put into context to understand how relevant it is. In the case of the statistics quoted by Manchester there is considerable doubt as to whether they can tell us anything positive or negative, but may point to things which Manchester needs to do better in its 20mph roll out. We list the main flaws and what may be learnt from them.

 

  1. The roads chosen for Phase one are atypical of the aggregate of Manchester roads. They comprise 20% of the roads in Manchester city yet before introduction of the 20mph limit these only comprised only 7% of vulnerable road users casualties compared to all roads. Some of the roads in Phase 1 may also have included previous 20mph schemes. Hence any comparison needs to take these differences into account. Subsequent analysis of the roads used in the report shows that many were previously 30mph roads with physical calming and hence were not reflective of a normal wide-area 20mph implementation.
  2. Police enforcement in Manchester has been almost non-existent. Whilst no-one expects police on every 20mph corner Greater Manchester Police have prioritised non-20mph roads over 20mph and have not issued one fixed penalty notice for breaking a 20mph limit in the last 12 months. The basis has been that these roads are already relatively safe (see 1) with their 20 limit. Note that Greater Manchester Police has not used the NDORS course available for 20mph limit education as an alternative to fines as used by other forces. Neither has it worked with Fire Services to ease manpower requirement in iniatives such as Kid's courts used by Merseyside and West Midlands police.
  3. The numbers used are not statistically significant. The Manchester report quotes a reduction from 7 pedestrian casualties in Moss Side and Fallowfield to 6 as a 14% reduction compared to a city-wide reduction of 29% (673 to 444). The confidence levels on such a small number as 7 are such that this is more likely due to random fluctuation than any trend. Even taking the whole of the Phase one area there were only 53 pedestrian casualties before implementation compared to 673 across the city. If 20% of roads have 53 pedestrian casualties and 100% across the city have 673 then if the 53 were replicated on the other roads that number would drop from 673 to 265 compared to the actual reduction to 444. The fact is that you cannot make valid comparisons between samples in the tens and those in the hundred.
  4. Manchester's roll-out has been far too slow and not shown the necessary commitment and vision. Phase 1 was commenced in 2012 yet Phase 2 has not yet been completed some 5 years later. This means that there is considerable variability across the city in the perceived limit on residential roads. Whilst cost is a burden for larger authorities, especially with out-of-date repeater signage requirements, April 16 regulations that leave repeaters to local authority discretion and halve the number of terminal signs required could have been used to rapidly progress a complete implementation across the city as minimal signage costs have fallen by about 70%. See our signs Briefing Sheet.
  5. The report admits that the data is flawed and inconclusive. The report actually says "we would need to evaluate data over a longer time to get data that is more statistically relevant." Indeed taking a similar broad brush approach without appropriate consideration of the detail could be considered careless. Taking as an example the national road casualty statistics for 2015 it appears that motorway crashes only reduced by 1% compared to previous years whereas the total for all GB roads reduced by 4%. Would we seriously consider "scrapping motorways" on the basis of such "evidence"? 

We are pleased that Manchester City Council is continuing its 20mph Phase 2 roll-out, however we believe that it has made a mistake in questioning the value of 20mph limits. Whilst there may be much for others to learn, it is probably more about how Manchester can implement 20mph limits more effectively rather than whether they should be doing it at all. 

We therefore look forward to Manchester City Council using the review of its implementation plans and gaining a more measured and statistically competent analysis of its current 20mph limits. This analysis should go far beyond looking only at vulnerable road user casualties and consider the wider public and public health benefits of lower limits. It should also come up with recommendations on how it needs to work with GMP and Fire Services for appropriate enforcement and far better public engagement. 

Councils in the North West such as Calderdale and Warrington are achieving real success in their wide-area 20mph implementations. These include casualty reductions of typically 20%, better and fairer sharing of roads, increased active travel and quieter neighbourhoods with a greater sense of community. Note that the biggest reductions were for car occupants who were specifically excluded from the Manchester report.

The Manchester experience needs to be put in perspective and recognised as a short-sighted reaction to some early, small number figures which are far from sound or significant. We would be pleased to meet with the cabinet member, Cllr Rosa Battle, to discuss a positive way forward in its plans to make Manchester roads a better place for all concerned and continue its plans for delivering 20mph limits across the whole city on places where people live.

Our recent Press Release is available also.

Showing 4 reactions

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  • commented 2017-07-31 21:46:13 +0100
    Hi Vanessa
    Our response is that driving more calmly and eliminating acceleration to 30mph will have a very positive effect on air quality. See our press releases

    20MPH LIMITS OFFER A TOXIC DIESEL FUME REDUCTION EQUIVALENT TO TAKING HALF OF ALL PETROL CARS AWAY
    http://www.20splenty.org/emission_reductions

    NICE RECOMMENDS 20MPH LIMITS WITHOUT TRAFFIC CALMING TO IMPROVE AIR QUALITY
    http://www.20splenty.org/nice_20mph_for_air_quality

    Rod
  • commented 2017-07-31 15:52:39 +0100
    What is your response to the argument that 20mph limits increase traffic pollution on our roads, where the air quality is already at dangerous levels? Air quality is a huge issue, especially in towns and cities.
  • commented 2017-03-13 16:19:33 +0000
    Dear anonymous person

    If you take 53 pedestrian casualties on 20% of the roads and scaled that up to 100% you would get 53 × 5 which is 265. Hence if the other roads had shown the same pedestrian statistics as the 20% then instead of being 673 across the city they would be 265.
  • commented 2017-03-13 14:16:52 +0000
    I don’t understand why 265 is being compared with 444 in point 3. The 673 would have only dropped to 533 (not to 265) if the “success” in the review areas was repeated across the city.