The Department for Transport (DfT) recently published the most authoritative study to date on the impact of wide-area signed-only 20 mph speed limits. It showed that there is no road safety benefit whatsoever from such schemes. In addition they have negligible impact on modal shift or on traffic speeds.

This is the long-awaited evidence that enormous amounts of money are being wasted on implementing 20 mph schemes which could have been spent instead on more effective road safety measures. In London alone, it is estimated that tens of millions of pounds have been spent on 20-mph signed-only schemes to no effect and nationwide it must run into hundreds of millions of pounds.

This disappointing result is very similar to the result of a study of driver education courses now being used by the police to generate funds. Both that and 20 mph schemes have been advocated by those who know little about road safety and have not studied the evidence. The Alliance of British Drivers (ABD) has long called for “evidence-based” road safety policies. The latest evidence should not be ignored.

One organisation that has been promoting 20-mph speed limits as the solution to road safety problems is “20s Plenty for Us” – see http://www.20splenty.org/ .

Their reaction to the report is to criticise the statistical analysis and the areas studied (both of which are unjustified) and suggest all that is needed is more enforcement. The fact that even active enforcement (e.g. in the City of London where hundreds of drivers have been fined for exceeding 20 mph with no impact on casualties) only reduces traffic speed by insignificant amounts is ignored.

The DfT report can be read here: https://www.gov.uk/government/publications/20-mph-speed-limits-on-roads . Key paragraphs from the report are:

“The evidence available to date shows no significant change in the short term in collisions and casualties, in the majority of the case studies (including the aggregated set of residential case studies).”

“Journey speed analysis shows that the median speed has fallen by 0.7mph in residential areas and 0.9mph in city centre areas.”

What has been happening is that the anti-car activists encouraged by 20s Plenty are now wasting millions of pounds nationwide when that money would have been better spent on other road safety measures – such as road engineering and education of younger drivers.

Note: the ABD is not opposed to the use of 20-mph speed limits where it might be of benefit or where compliance will be high but it is not the solution to all road safety problems and simply sticking up signs is a waste of money. The simplistic solutions proposed by 20s Plenty and others cannot and does not work to reduce the Killed and Seriously Injured on our roads to any major extent.

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