Support for blanket 20mph limits isn’t as universal as campaigners claim

Malcolm Heymer is traffic management adviser for the Alliance of British Drivers, and a retired highway, traffic and road safety engineer with over 30 years` local authority experience.

Malcolm Heymer is traffic management adviser for the Alliance of British Drivers, and a retired highway, traffic and road safety engineer with over 30 years` local authority experience.

The campaign group 20’s Plenty for Us issued a press release last month to mark the publication of a briefing note by the Local Government Information Unit (LGiU), entitled Area-wide 20mph neighbourhoods: a win, win, win for local authorities. Subsequently, Anna Semlyen, 20’s Plenty’s campaigns manager, wrote in LTT in favour of making 20mph the national speed limit in street-lit areas (LTT 19 Dec 13).

Clearly, the proponents of blanket 20mph speed limits are trying to create the impression that the evidence is overwhelmingly in their favour and the momentum for a reduction in the urban speed limit is unstoppable. This must not be allowed to go unchallenged.

The title of the LGiU briefing note suggests a very one-sided analysis and this is confirmed when reading it. While 20’s Plenty describes the report as “independent”, it contains frequent references to 20’s Plenty for Us and other organisations unsympathetic to motor vehicle users.

The report makes much of the claimed benefits of 20mph limits in terms of public health, safety etc, but makes virtually no mention of the impact on drivers. The author clearly does not understand the correct use of speed limits or how drivers vary their speed according to changing conditions, which is an intuitive and non-numeric process. This is why reductions in speed limit produce a far lower impact on driven speeds (typically around 1mph where 30mph limits are reduced to 20mph).

Some of the claims in the LGiU report are very shaky. One, from Bristol City Council, states that walking and cycling increased on average by 23 and 20.5% respectively after 20mph limits were introduced. Results elsewhere have shown very little change in walking or cycling in 20mph areas, so I investigated the Bristol figures and discovered they came from a council report in July 2012. That report states that walking increased by between 10 and 36%, and cycling by between 4 and 37%. So the claimed average increases were calculated by adding the highest and lowest percentages and dividing by two!  Such an appalling misuse of statistics does not inspire confidence.

Another dubious claim is from a 2011 British Social Attitudes Survey, in which 73% of those surveyed were said to favour 20mph limits for residential roads.  Several factors could influence this result, not least the wording of the question and respondents’ understanding of ‘residential road’. Most people are unaware that speed limit reductions achieve a much lower fall in actual speeds, so will have a mistaken view of what a 20mph limit would achieve. There is also the phenomenon of people giving what they think is the ‘virtuous’ answer to an opinion poll.

As any police officer who enforces speed limits will confirm, whenever residents demand a lower limit, among the first to be caught exceeding it will be those who campaigned for it in the first place. People are very ambivalent about speed limits and an opinion poll finding should be taken with a large pinch of salt. It should certainly not be assumed to support a blanket change from 30 to 20mph.

Despite the assertions of 20’s Plenty and others, by no means all local authorities are itching to impose blanket 20mph limits. Indeed, in Anna Semlyen’s own authority of York, Lib Dem councillors oppose area-wide use (LTT 26 Jul 13). Norfolk has rejected them (LTT 4 Oct 13) and so has Kirklees (LTT 19 Dec 13).  Even in Green-dominated Brighton, the council’s 20mph ambitions have been curtailed (LTT 19 Dec 13).

It is claimed by 20’s Plenty that changing the default limit to 20mph would halve the cost to councils of imposing the lower limit area-wide. However, this ignores the massive additional cost that would be imposed on those councils that do not wish to follow the 20mph blanket approach. DfT figures on road length suggest there are probably some 70-75,000 miles of urban, street-lit road in England and Wales with the default 30mph limit. Even if half this mileage consists of narrow residential roads where 20mph may be an appropriate limit (unlikely), the cost of re-signing the other half, and all the junctions between 30mph and 20mph roads, would be prohibitive. This is probably what 20’s Plenty is banking on – that most local authorities would roll over and submit to their extreme view. So much for local choice! It must not be allowed to happen; the DfT must remain resolute in retaining the 30mph urban limit.

Where 85th percentile speeds exceed 20mph by a significant margin, lowering the speed limit from 30mph should never be considered. On roads where speeds are already below 20mph, what is achieved by introducing a 20mph limit? Speeds will barely change but a false sense of security may be created, which probably accounts for the increases in some types of casualty seen in many of the schemes already implemented.

The proponents of blanket 20mph limits are invariably found in that part of the political spectrum that promotes regulation of all aspects of everyday life and abhors the freedom of choice that cars provide. The ABD, on the other hand, believes in personal choice and individual responsibility. The success of well designed shared-space schemes shows that road safety can be enhanced when controls and priorities are removed and individual road users are made to think for themselves. This must surely be a better and more acceptable approach than heavy-handed, over-regulation.  

Have your say about 20mph limits at LTT's 'Time for 20mph' conference on the 18 February