Question to the Department for Transport:

To ask His Majesty's Government whether they have observed a reduction in death and injury caused by road traffic accidents in areas, such as central London, which have introduced a 20 miles per hour speed limit.

The Department for Transport published a comprehensive three-year evaluation of the effect of 20mph limits, which are 20mph schemes relying only on signage, on 22 November 2018.

The evaluation looked at twelve case studies including two in city centres (Brighton and Winchester). No case studies were in London.

It found insufficient evidence to conclude that that there had been a significant change in collisions and casualties following the introduction of 20mph limits in residential areas.

The only case study area showing a significant change in collisions and casualties, relative to its 30mph comparator area, was Brighton City Centre. This scheme covered both major and minor roads, with a 19% reduction in overall casualties, a 29% reduction in pedestrian casualties and a 51% reduction in casualties aged 75 or over. No significant change in casualties of cyclists or under 16s was found.

The evaluation stated that the changes appeared to be a reflection of the city characteristics, and the blanket implementation of 20mph limits across all roads within the scheme area, including higher flow A and B roads which were typically excluded from the residential case study schemes. There was a significant reduction in collisions across all road types, but the change was most pronounced on major strategic roads. The evaluation stressed that this represented just one case study, and the extent to which the findings were transferable to other locations was unclear.