Question to the Department for Transport:

To ask His Majesty's Government whether the 20 mile per hour speed limit in central London is primarily to (1) reduce accidents, or (2) raise revenue; and if the former, what data they hold for any reduction in mortality since the introduction of that speed limit.

Responsibility for decisions on most of the London road network rests with the London boroughs, while Transport for London (TfL) is responsible for the Red Routes. The introduction of 20mph speed limits on all these roads is a matter for local determination, either by Boroughs or TfL, and the Department does not intervene in those decisions.

The Department’s comprehensive three-year evaluation of the effect of 20mph signed-only limits was published on 22 November 2018. It substantially strengthened the evidence base on perceptions, speeds and early outcomes associated with 20mph speed limits. The evaluation can be viewed online.

A London study published on the TFL website shows 35% fewer collisions, 34% fewer fatal/serious injuries, and 46% fewer child casualties on 20‑mph roads.