Question to the Department for Transport:

To ask the Secretary of State for Transport, whether he has made an assessment of the potential impact of 20mph speed limits on the safety of motorists.

The Department for Transport published a comprehensive three-year evaluation of the effect of 20mph signed-only limits on 22 November 2018; this may be found here. The evaluation considered collision and casualty statistics for all road user types. It showed that typically they resulted in less than a 1mph reduction in average speed.