Guidance

TAG data book

Historical and reference information on all the appraisal and modelling values referred to in the transport analysis guidance (TAG).

• From: Department for Transport
• Published: 29 November 2018
• Last updated: 28 May 2026
  Show all updates

  1. 28 May 2026

     TAG data book updated.

  2. 16 April 2026

     Added forthcoming changes on appraisal, electric vehicle mileage share, Green Book, occupancy and journey purpose split updates.

  3. 18 December 2025

     Added 'Forthcoming change: updates to road freight values of travel time'.

  4. 11 December 2025

     Tag data book updated.

  5. 16 October 2025

     Added forthcoming change: appraisal data update.

  6. 29 May 2025

     TAG data book updated.

  7. 17 April 2025

     Added 'Forthcoming change: appraisal data update'.

  8. 28 November 2024

     TAG data book updated and forthcoming changes for May 2025 added.

  9. 17 October 2024

     Added 'Forthcoming change: updates to economic and demographic data and clarified guidance on rail appraisal'.

  10. 30 May 2024

      Unit updated and May 2024 forthcoming change note removed.

  11. 25 April 2024

      Forthcoming changes added.

  12. 30 November 2023

      TAG data book updated.

  13. 19 October 2023

      Added forthcoming change about appraisal guidance updates.

  14. 6 October 2023

      Added forthcoming change about carbon valuation.

  15. 31 May 2023

      TAG data book updated.

  16. 19 April 2023

      Added forthcoming change: spring 2023 data book and guidance updates.

  17. 18 January 2023

      TAG data book updated.

  18. 30 November 2022

      TAG data book updated.

  19. 19 October 2022

      Forthcoming changes for November 2022.

  20. 16 June 2022

      Tables A1.3.11 and A1.3.12 in 'TAG data book: fleet assumptions' have been corrected to reflect the addition of electric PSV energy consumption parameters.

  21. 30 May 2022

      Updated TAG data book. Added data book: fleet assumptions, and a forthcoming change note on fleet assumptions.

  22. 29 April 2022

      Forthcoming change to guidance note added, the note details guidance alterations to be implemented in May 2022.

  23. 29 November 2021

      Updated TAG data book.

  24. 13 October 2021

      Notification of forthcoming change for November 2021.

  25. 11 October 2021

      Added forthcoming change data book with updated carbon values and marginal external costs.

  26. 30 July 2021

      Added latest version of TAG data book and removed sensitivity testing document.

  27. 19 May 2021

      Added forthcoming change to TAG data book.

  28. 23 July 2020

      Added new data book: TAG data book - sensitivity training.

  29. 9 July 2020

      Annual Parameters source note corrected to refer to source material referenced in November 2019 forthcoming change, and outturn data based on ONS March 2020 publications. Marginal External Costs corrected for weighted average of congestion bands (A5.4.1), band 5 London motorways (A5.4.2), and Scotland values (A5.4.4). Environmental analysis tables corrected for fuel/electricity price forecasts and fleet splits by fuel type. Average value of accident prevention per casualty (A4.1.1).

  30. 29 May 2020

      Update to outturn and forecast data for GDP, inflation and average earnings, based on estimates from the ONS and projections from the OBR (due to be published alongside Autumn budget); update to the forecast values for Marginal External Costs based on estimation by the Department’s National Transport Model. Tables A5.4.1 - A5.4.4 will be updated as a result; update to the professional drivers’ values of time to reflect latest Annual Survey of Household Earnings data.

  31. 22 October 2019

      October 2019 forthcoming changes document added.

  32. 11 July 2019

      Corrected light goods vehicles formulas in table A1.3.10a.

  33. 4 June 2019

      TAG Data Book re-published with slight correction affecting the look-up year in sheet A1.3.7.

  34. 31 May 2019

      Updated reflecting the forthcoming changes given new forecasts from the ONS and OBR.

  35. 1 May 2019

      2019 forthcoming changes document added.

  36. 29 November 2018

      First published.

Documents

TAG data book

5.75 MB

This file may not be suitable for users of assistive technology.

Request an accessible format

If you use assistive technology (such as a screen reader) and need a version of this document in a more accessible format, please email webmasterdft@dft.gov.uk. Please tell us what format you need. It will help us if you say what assistive technology you use.

Details

The TAG data book provides all of the appraisal and modelling values referred to in TAG guidance. The data book features historical information and factual reference information about the appraisal and modelling values.

The previous version, TAG data book v2.02, was released in December 2025.

TAG provides information on the role of transport modelling and appraisal, and how the transport appraisal process supports the development of investment decisions to support a business case.