20mph speed limits are effective, study finds

Issue date: 13 February 2018


20mph speed limit area on Whiteladies road in Bristol

A new study published today, The Bristol Twenty Miles Per Hour Limit Evaluation (BRITE) Study by the University of the West of England (UWE Bristol), has found that 20mph speed limits lead to important reductions in average traffic speeds, and are associated with very promising improvements in road safety.

Analysis by a team of researchers at UWE Bristol has revealed that average traffic speeds in the city of Bristol reduced by 2.7mph on roads where the 20mph speed limit was introduced. Annual rates of road traffic casualties over the same period also reduced, with an estimated total number of injuries avoided across the city of four deaths, eleven serious injuries, and one hundred and fifty-nine slight injuries. The estimated annual saving following the casualties avoided is just over £15 million pounds, based on a Department for Transport formula.

The report's lead author Dr Paul Pilkington, Senior Lecturer in Public Health at UWE Bristol said, “In January 2014 Bristol began to introduce 20mph speed limits throughout the city, following the completion of successful pilot schemes in South and East Bristol. The 20mph speed limit was introduced in six phases, with the process being completed in September 2015. The roll-out of the 20mph speed limits in Bristol was about more than reducing road traffic casualties, although this was one of the aims. It also sought to improve health and wellbeing across the city, taking a wider perspective as to how slower traffic speeds might impact on people's lives.

“UWE's research took a public health approach to the evaluation, using a variety of data sources to examine: changes in vehicle speeds; road traffic casualties; levels of walking and cycling; public perceptions and attitudes; and reported levels of health and wellbeing across the communities in Bristol, before and after the introduction of the 20mph speed limits.

“The reduction in speeds is larger than seen in previous evaluations. Our study was a more sophisticated analysis than previous studies, using speed data from over 36 million vehicle observations and controlling for other factors that might affect changes in traffic speeds.

“The reductions in speeds and road traffic casualties are a very promising finding for the city, and for 20mph speed limits in general. It offers a model for other towns and cities across the world, who are seeking to reduce traffic speeds, cut road traffic casualties, and promote community health and wellbeing through road danger reduction.”

The full report The Bristol Twenty Miles Per Hour Limit Evaluation (BRITE) Study can be downloaded from the UWE Research Repository at: http://eprints.uwe.ac.uk/34851/

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