20mph more effective when accompanied by traffic calming

25 May 2023

Different ways of reducing vehicle speeds in urban areas have been in use in the UK and mainland Europe for decades. Their effectiveness has not always been fully understood. PACTS latest research has shed light on the situation. It confirms that 20mph limits backed by physical measures have substantially greater speed and casualty reduction benefits than those without.

Building on research in The Road Safety Observatory and elsewhere, the project, ‘Lower urban speed limits in Europe – what does the evidence show?’ (LUSTRE), involved a collaboration of road safety experts, including Professor Mohammed Quddus (Imperial College London) and Dr Akis Theofilatos (Loughborough University), Dr Rune Elvik (Institute of Transport Economics, Norway), Professor Lars-Christer Hyden (Lund University, Sweden), Ellen Townsend and Jenny Carson (European Transport Safety Council). It has been made possible with a grant of £60,000 from the Road Safety Trust.

The report opens with the development of speed limit-setting policy and methods in the UK. The history and impact of speed-reducing methods in France, Germany, The Netherlands, Norway, Sweden and Switzerland follows. Findings from a systematic review and classification of UK studies, known as meta-analysis, make up the third part of the report.
Findings are that the extent to which 20mph schemes deliver actual speed and casualty reductions depends on whether they are supported by other measures, such as road humps and/or changes in relative road width.

The report notes that further studies of the impact of area-wide speed limits will give more insights. Intelligent Speed Assistance (ISA) could, ultimately, be the most effective way of delivering actual reductions in speed and casualties.

The full report is available on The Knowledge Centre