There have been many calls to reduce speed limits on urban roads, which in London is of course most of the roads. That includes demands for the introduction of wide-area 20 MPH speed limits - often “signed only” ones with no accompany road engineering measures. Their effectiveness is very questionable though. The ABD is not opposed to 20 MPH speed limits on residential streets and where the normal speed of traffic is closely aligned so that compliance will be high. But we question the enormous expenditure on wide-area schemes which might have minimal impact on average speeds and on road traffic accidents. Clearly the money spent on them would be better spent on other road safety programmes or measures.

The following are some of the past articles we have published on this subject in London (click on to access the pdf document) which cover some of the available evidence:

Response to GLA Inquiry in 2008

Portsmouth 20 MPH Zones - published in 2010

20 MPH Zone Impacts - published in 2012

20 MPH Speed Limits - Historic Evidence - published in 2012

There were a number of articles published on the ABD London Blog in 2017 on the impact of 20 mph speed limits. Some of them are here:

For more information on a typical 20 MPH wide area scheme and its costs, go to this page for details of a campaign against one in the London Borough of Croydon: Croydon20

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