Introducing a 20mph speed limit in Glasgow

In 2020, Glasgow City Council undertook an assessment of how well a 20mph speed limit was working in 82 areas where it had been implemented. This showed that there had been a 31% reduction in casualties on these streets – a measure of its success.

Using this evidence, they decided to standardise the 20mph speed limit on streets near houses and schools, in busy centres, or with a high level of pedestrian or cyclist use.

This is a good example of how the performance of an existing policy can be measured and, if deemed successful, used to guide further action.