TAG data book

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


TAG data book


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 was released in May 2021.

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.

Published 29 November 2018
Last updated 30 July 2021
  1. Added latest version of TAG data book and removed sensitivity testing document.

  2. Added forthcoming change to TAG data book.

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

  4. 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).

  5. 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.

  6. October 2019 forthcoming changes document added.

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

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

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

  10. 2019 forthcoming changes document added.

  11. First published.