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Guidance

TAG unit A3 environmental impact appraisal

Guidance on the analysis of environmental impacts in transport appraisals.

From:
Department for Transport
Published:
31 May 2019
Last updated:
5 November 2026 — See all updates

Documents

TAG unit A3 environmental impact appraisal

PDF, 1.11 MB, 118 pages

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Forthcoming change: discount rate changes in TAG

https://www.gov.uk/government/publications/forthcoming-changes-and-previous-versions-of-tag/forthcoming-change-discount-rate-changes-in-tag

Forthcoming change: the scope of international aviation and shipping greenhouse gas emissions to be reported in appraisals

https://www.gov.uk/government/publications/forthcoming-changes-and-previous-versions-of-tag/forthcoming-change-the-scope-of-international-aviation-and-shipping-greenhouse-gas-emissions-to-be-reported-in-appraisals

Details

This document gives guidance on environmental impact appraisal.

The previous version of this guidance was published 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.

Updates to this page

Last updated:
5 November 2026
Show all updates

  1. Added forthcoming changes, which are expected to be released in December 2026.

  2. TAG unit A3 updated.

  3. Added forthcoming changes on appraisal update.

  4. TAG unit A3 updated.

  5. Added forthcoming change: vehicle emissions carbon tool. .

  6. Updated TAG unit A3.

  7. Updated with forthcoming changes for May 2025.

  8. TAG unit A3 updated.

  9. Forthcoming changes added.

  10. TAG unit A3 guidance updated.

  11. Added forthcoming change about appraisal guidance updates.

  12. Added forthcoming change about carbon valuation.

  13. TAG unit A3 guidance updated.

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

  15. Unit A3 guidance updated.

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

  17. Updated with new version of unit A3 guidance.

  18. Updated TAG unit A3 guidance.

  19. NO2 changed back to NOx in 3.2.7 following Department for Environment, Food & Rural Affairs clarification.

  20. Information updated for technical errors NOx changed from NO2 in 3.2.7 and 3.4.4.

  21. First published.

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