Question to the Department for Transport:

To ask Her Majesty's Government whether there has been a reduction in road traffic deaths in the first year of operation of a 20mph limit in those London boroughs that have reduced their speed limit from 30mph.

Information on road traffic deaths in London boroughs is not collected by the Department for Transport in the form requested, because the Department does not hold information on which London boroughs have implemented 20mph limits, nor when the limits were installed.

The Government has not conducted any specific research into levels of pollution produced by a new 20mph limit in the relevant London boroughs. The air quality plan for tackling roadside nitrogen dioxide concentrations in the Greater London Urban Area published in July 2017 provides details of measured nitrogen dioxide concentrations in London between 2001 and 2015.