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Guidance

Road congestion and travel time statistics information

Guide to road congestion and travel time statistics, their source documents, notes and definitions plus supporting technical documents.

Updates to this page

From:
Department for Transport
Published:
11 August 2016
Last updated:
30 September 2026
Show all updates

  1. Updated BQR text. Updated Local A Imputation table to June 2026.

  2. Updated the Background Quality Report and the imputation table to reflect Great Britain and data to March 2026.

  3. Added imputation data to December 2025, and a new methodology note to discuss changes within a sample.

  4. Data for imputation table up to September 2025 has been added

  5. Data imputation up to June 2025 added to local a quality table. Pre-release access list updated.

  6. Addition of data for January to March 2025 to local a data quality table.

  7. Data added to include information up to December 2024.

  8. Data up to September 2024 has been included in the 'Percentage of data imputed for travel time statistics on the local 'A' road network, by month' table.

  9. Data for April to June 2024 have been added to the 'Percentage of data imputed for travel time statistics on the local 'A' road network, by month' table, and revisions have been made to the series following agreements with suppliers to improve consistency going forward.

  10. Data up to March 2024 has been added to the Local A data quality table.

  11. Over 2023 the congestion statistics processing was transferred to a new software enabling greater precision and accuracy in calculations and imputation of the production of statistical values. This has led to minor revisions for 'Percentage of data imputed for travel time statistics on the local 'A' road network, by month'

  12. Data table for the percentage of data imputed for travel time statistics on the local 'A' road network, by month has been updated.

  13. Data table for the percentage of data imputed for travel time statistics on the local 'A' road network, by month updated with the latest data.

  14. The percentage of data imputed for travel time statistics on the local 'A' road network, by month' table has been updated to include data from April 2022 to March 2023.

  15. The 'Percentage of data imputed for travel time statistics on the local 'A' road network, by month' table has been updated to include data from January 2019 to December 2022

  16. The local A road imputation table has been updated to included data to September 2022.

  17. The 'Percentage of data imputed for travel time statistics on the local 'A' road network, by month' has been updated to include data to June 2022.

  18. A new HTML document discussing the impact of the coronavirus (COVID-19) pandemic on flow weighting has been added.

  19. A new background quality report has been produced to reflect the change in data suppliers and data processes.

  20. Percentage of data imputed for travel time statistics on the local 'A' road network, by month data table updated.

  21. New methodology added.

  22. SRN and local 'A' roads imputation tables updated for the year ending March 2021. Pre-release access document updated.

  23. SRN and local 'A' roads imputation tables updated for the year ending December 2020 and pre-release access document updated.

  24. SRN and local 'A' roads imputation tables updated for the year ending September 2020.

  25. Pre-release access page added, SRN and local 'A' roads imputation tables updated for the year ending June 2020.

  26. SRN and local 'A' roads imputation tables updated for the year ending March 2020.

  27. National Statistics designation page for road reliability and congestion added. Data tables for the Strategic Road Network and local 'A' roads updated for the 2019 travel time measures report.

  28. Updated imputation tables for 'Travel time measures for the Strategic Road Network and local ‘A’ roads: July 2018 to June 2019'.

  29. SRN and local 'A' roads imputation tables updated for the year ending March 2019.

  30. SRN and local 'A' roads imputation tables updated for the 2018 report.

  31. Local roads and SRN monthly data tables updated for the year ending September 2018.

  32. Local roads and Strategic Road Network monthly data tables updated for the year ending June 2018.

  33. Local roads and SRN monthly data tables updated.

  34. Local roads and SRN monthly data tables updated for the year ending December 2017.

  35. Local roads and SRN monthly data documents updated.

  36. Local roads and SRN monthly data documents updated.

  37. Local roads and SRN monthly data documents updated.

  38. SRN, Highways England and local speed data documents updated.

  39. Local roads and SRN monthly data documents updated.

  40. Local roads and SRN monthly data documents updated.

  41. First published.

Applies to England, Scotland and Wales

Documents

Travel time statistics background quality report

HTML

2025 Break in the Local A road series: Methodology note on the implications of a sample change for the Local A road Congestion statistics

HTML

Impact of the Coronavirus (COVID-19) pandemic on flow weighting for congestion data

HTML

Impact of Changing Strategic Road Network Data Source

HTML

Impact of Changing Local 'A' Roads Data Source

HTML

Accredited official statistics status of road reliability and congestion

HTML

Travel time measures for the Strategic Road Network and local ‘A’ roads: pre-release access

HTML

Percentage of data imputed for travel time statistics on the local 'A' road network, by month

ODS, 9.07 KB

This file is in an OpenDocument format

Travel time historical statistics background quality report

PDF, 1.9 MB, 13 pages

Details

Tables displaying the level of imputation for historic data tables CGN01, CGN02, CGN09 and select CGN04 and CGN05 are no longer available, as the relevant tables are no longer produced.

Road congestion and travel time statistics notes and definitions and other source documents.

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