Question to the Department for Transport:

To ask Her Majesty's Government (1) how traffic congestion has been monitored in England, (2) what data they have collected, and (3) what data they have published, about such monitoring since 2015.

The Department for Transport produces statistics on road congestion on the Strategic Road Network (SRN) and local ‘A’ roads in England. These statistics, used to monitor road congestion and journey time reliability, are compiled from journey time data from in-vehicle global positioning systems (GPS).

The statistics report two measures of congestion- average speed as an estimate of the physical level of congestion and average delay which is the difference between speed limit (SRN) or free flow (local ‘A’ roads) travel times and average journey times.

Statistics from April 2015 onwards for congestion on the SRN and January 2014 onwards for local ‘A’ roads are published online as part of the 'Road congestion and travel times' collection on gov.uk.