The Bristol Twenty Miles Per Hour Limit Evaluation (BRITE) Study

This study aimed to evaluate the impact of the roll-out of 20mph speed limits across the city of Bristol. The research took a holistic, public health approach to 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 city.

The study found statistically significant reductions in average traffic speeds of 2.7mph across the city of Bristol, following the introduction of 20mph speed limits. This is a larger reduction than seen in previous evaluations in other cities.

The study employed a more sophisticated analysis than previous studies of 20mph limits, including using individual speed data from over 36 million vehicle observations and controlling for other factors that might affect changes in traffic speeds.

There has been a reduction in the number of fatal, serious and slight injuries from road traffic collisions, equating to estimated cost savings of over £15 million per year.

Although there is still majority support for 20mph speed limits in Bristol, there remains concern about compliance and behaviour of other drivers. Only 13%-20% of people thought that speeds had decreased on their street.

Walking and cycling across Bristol has increased, both among children travelling to school and adults travelling to work. However, it was not possible to assess whether these trends related to the 20mph speed limit intervention.

In order to assess effectiveness of 20mph speed limits, it is vital that other towns and cities follow Bristol’s example, and prioritise the ongoing collection and analysis of appropriate data on vehicle speeds, road traffic casualties and wider public health impacts.