National Statistics Status of Road Reliability and Congestion
Updated 7 March 2024
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National Statistics status
National Statistics status means that our statistics meet the highest standards of trustworthiness, quality and public value, and it is our responsibility to maintain compliance with these standards.
The designation of statistics on Road Reliability and Congestion Statistics as National Statistics was confirmed in July 2012 following a full assessment against the Code of Practice by the Office for Statistics Regulation. The methodology changes in 2015 to 2016 was reviewed by UKSA and deemed as not requiring a formal re-assessment.
Changes to these statistics
Since the latest review by the Office for Statistics Regulation, we have continued to comply with the Code of Practice for Statistics, and have made the following improvements:
- changes to the ‘on time reliability measures’ were introduced in May 2015, replacing them with the Planning Time Index used currently to calculate SRN reliability
- subsequent changes were made to the Local ‘A’ Road measures in March 2016 to provide a more complete picture that would align better with the data produced for the Strategic Road Network
- average speed and delay statistics were expanded to include all hours in May 2016 and replaced the ‘Average speeds during the weekday morning peak’ which exist up to December 2015
- revisions to the vehicle classification file used to process the data were published in February 2019, with all data for 2018 being reprocessed
- a background quality report was published in September 2022, which sets out the methodology, quality of data, and uses for the data
- due to changes in the underlying road traffic statistics data used to weight the Local ‘A’ Road metrics. There has been a step-change introduced (PDF, 315KB) in the 2019 data