This page is an at-a-glance summary of the current TAG units, and what was new in the last update of each unit. May 2025 updates are highlighted. Clicking on the date of the current version will take you to the unit itself.
I will try to keep it up to date, but for anything vital you should always check DfT’s TAG webpages to confirm the latest position and the full content of the guidance.
Updated to 30 May 2025.
Jump to:
- TAG units
- TAG general and supplementary guidance
- TAG databooks, worksheets, summary tables and other spreadsheet files
- TAG software tools
TAG units
| Unit | Title | Previous version | Current version (and any forthcoming changes) | |
| Date | What’s new | |||
| Appraisal (A) units | ||||
| A1 Cost-benefit analysis | ||||
| A1-1 | Cost-benefit analysis | Nov 2023 | May 2025 | · Base year (for both prices and values) updated from 2010 to 2023 · Appendix C (worked example of calculating present values) updated accordingly |
| A1-2 | Scheme costs | May 2024 | May 2025 | · Base year (for both prices and values) updated from 2010 to 2023 · Threshold for requiring QRA (para 3.1.1) updated accordingly from £5m (base cost in 2010 prices) to £7m (base cost in 2023 prices) · Table 7 (OB uplift percentages) has new advice on when the fixed-links rate may be appropriate for active mode schemes |
| A1-3 | User and provider impacts | May 2022 | May 2025 | · References to 2010 base year removed · 4.3.2 (values of non-working time) clarifies that the values are reported in base year values · 4.5.2 (VOTs for appraisal purposes increase by 1.5% annually) removed · New 5.1.2 – 5.1.3 and 5.1.12 – 5.1.16 on the new two-stage process for valuing changes in fuel costs, taking account of non-variable costs, with the long-run variable cost (LRVC) as the final measure. Appendix A (user benefit calculation) updated accordingly · 6.2 (JTR on inter-urban motorways and dual carriageways) has reverted to the pre-2022 wording [not clear whether this is intentional] · New Appendix D with the guidance on large cost changes in appraisal, previously in the TUBA General Guidance and Advice. · 2.1.10-2.1.11 (large cost changes and new modes) updated reference to new Supplementary Guidance |
| A2 Economic impacts | ||||
| A2-1 | Wider economic impacts appraisal | Nov 2024 | May 2025 | · Updated cross-references to the revised unit M5.3 (SEM) · Minor edits for clarity and formatting · Revised definition of ‘transformational scheme’, including “smaller schemes that can be transformative at a local level” (Appendix A glossary) |
| A2-2 | Induced investment | Nov 2024 | May 2025 | · Clarified and expanded definition of dependent development (DD) (section 3.1 and new 3.2) · Additional guidance on how uncertainty around DD benefits should be considered in the economic narrative (new 3.1.23) · New sensitivity test about the level of delivery of the assumed DD (new 3.5, Box 2 and Appendix C) · Updated cross-references to the revised unit M5.3 (SEM) · Minor edits for clarity and formatting |
| A2-3 | Employment effects | Nov 2024 | May 2025 | · Updated cross-references to the revised unit M5.3 (SEM) · Minor edits for clarity and formatting |
| A2-4 | Productivity impacts | Nov 2024 | May 2025 | · Updated cross-references to the revised unit M5.3 (SEM) · Minor edits for clarity and formatting |
| A3 Environmental impacts | ||||
| A3 | Environmental impact appraisal | May 2024 | May 2025 | · 3.4.10 reference to 2010 base year removed · Textual cross-references to tables appear to have become erroneous; table numbers themselves have not changed |
| A4 Social and distributional impacts | ||||
| A4-1 | Social impact appraisal | May 2022 | Nov 2022 | · 2.3.15-16 updated re safety benefits of rail interventions · 3.2.13 updated willingness-to-pay quality-adjusted life years (WTP-QALY) value · 3.2.18 Changed method of growing absenteeism values. [was an April 2022 FC] |
| A4-2 | Distributional impact appraisal | May 2023 | May 2024 | Noise: New 3.4.10 about potential differences in affected-population estimates between the DI method and the noise valuation workbook method |
| A4-3 | Place-based analysis | n/a | Nov 2022 | New unit |
| A5 Uni-modal appraisal | ||||
| A5-1 | Active mode appraisal | May 2020 | Nov 2022 | Update to cycling diversion factors |
| A5-2 | Aviation appraisal | Nov 2023 | May 2025 | 3.3.3 Updated to reflect carbon price assumptions for aviation emissions under CORSIA being included in the Databook |
| A5-3 | Rail appraisal | May 2024 | May 2025 | · 2.5.7 updated guidance on applying OB uplift to rail opex · Table 3 (OB adjustments) new entries for stations and terminal buildings capex [not previously announced, nor published in the FC version] · Table 5 reference to price/value base year removed · 3.7.2 removed reference to use of the freight grants calculator for calculating road freight distance |
| A5-4 | Marginal external costs | Nov 2021 | May 2023 | · New 2.2.3 (p4) highlighting that the diversion factors (other than rail) are in person-km and need factoring for car occupancy · 2.3.4 & 2.4.8 (p7-8) updated to reflect the new years in databook v1.21 · 2.5.3 (p9) (extrapolation beyond last forecast year) advice changed · 2.5.5 (p9) (discounting) added that all components of MECs should use the standard discount rate, as the effect of the lower health rate has already been approximated where relevant · 2.6.1-2 (p9) (MECs in alternative scenarios) updated with the new years and reference to CAS · Appendix B (worked example) updated to reflect databook v1.21 |
| A5-5 | Highway appraisal | Possibly Oct 2013 | Jan 2014 | [not recorded here] |
| Modelling (M) units | ||||
| M1 modelling principles | ||||
| M1-1 | Principles of modelling and forecasting | Jan 2014 | May 2024 | General refresh and expansions, including: · Expanding section 1.1 to cover broader purposes of transport modelling and forecasting · Clarifying the key concepts and principles (sections 2, 3, 4, and 5) · Updating figure 1 (the standard transport model structure) · Adding explanation of multi-modal vs uni-modal approaches · Adding re use of ABM (section 4) · New section on modelling active travel and new mobility (section 4) · Changing the term ‘mitigating risks’ into ‘quality assurance’ (sections 4 and 5) and expanding guidance on quality assurance · New section on reporting requirements and potential checks / reviews · Minor clarifications throughout |
| M1-2 | Data sources and surveys | May 2020 | May 2024 | Restructuring, plus general update and clarifications. Including: · Adding re new data sources and their use cases · Updating and correcting advice and references on existing data sources · Clarifying advice on the suitability and quality of data · Minor clarifications throughout |
| M2 Demand modelling | ||||
| M2-1 | Variable demand modelling | May 2020 | May 2024 | Clarifications, plus updates to some parameters. Including: · Updates to the illustrative parameters for destination choice and mode choice (section 5.6) · New demand elasticity values for realism testing (section 6.4 and Appendix A) · Clarifying advice on the assessment of the need for VDM, the matrix form to use (OD vs PA) and the appropriate % gap formula for cost averaging model · Minor clarifications throughout |
| M2-2 | Base year matrix development | n/a | May 2020 | New unit [Note: unit M2-2 did not change in the May 2024 updates] |
| M3 Assignment modelling | ||||
| M3-1 | Highway assignment modelling | May 2020 | May 2024 | New appendix on how the guidance can be applied to using microsimulation for motorised highway modes. Including: · Introduction to microsimulation · References to existing guidance and best practice for microsimulation · Its potential role in scheme appraisal, including using it in combination with a more traditional approach |
| M3-2 | Public transport assignment modelling | May 2020 | May 2024 | Restructured and expanded. Including new or additional advice on: · The role of PT assignment in the overall model structure · Aspects of model development · Calibration and validation · Convergence · Reporting requirements |
| M4 Forecasting | ||||
| M4 | Forecasting and uncertainty | May 2023 | Nov 2023 | 9.1.5 (p.42) updated to reflect release of Tempro 8.1 (Sept 2023) which re-enables the ‘traffic growth from the NTM’ function |
| M5 Advanced modelling techniques | ||||
| M5-1 | Modelling parking and park-and-ride | Possibly Oct 2013 | Jan 2014 | New in the restructured TAG. Material previously in unit 3.10.7. |
| M5-2 | Modelling smarter choices | Possibly June or Oct 2013 | Jan 2014 | [not recorded here] |
| M5-3 | Supplementary economic modelling | Nov 2024 | May 2025 | Major revision to improve the guidance and reflect latest developments in SEM |
| M5-4 | Agent-based methods and activity-based demand modelling | n/a | May 2024 | New unit. Provides an introduction to these methods. Illustrates where they could be considered and how they can feed into an evidence base. Not guidance on, or approval for, their use in appraisal. |
| Evaluation (E) units | ||||
| E1 evaluation | ||||
| E-1 | Evaluation | n/a | Nov 2022 | New unit |
TAG general and supplementary guidance
| Title | Previous version | Current version (and any forthcoming changes) | |
| Date | What’s new | ||
| General guidance | |||
| TAG Overview | n/a | Jan 2014 | New for the restructured TAG |
| TAG Guidance for the Senior Responsible Officer | Dec 2017 | May 2018 | [Not recorded here] |
| TAG Guidance for the Technical Project Manager | Dec 2017 | May 2018 | [Not recorded here] |
| The Transport Appraisal Process | Jan 2014 | May 2018 | [Not recorded here] |
| Spending Objective Analysis | n/a | Nov 2023 | New document. Guidance on spending objective analysis: assessing options in terms of relative and absolute performance against a proposal’s spending objectives. Covers objective-setting, the long-list and short-list stages, reporting the impacts in the Spending Objective Analysis Statement (SOAS), and the link with evaluation. [Was an Oct 2023 FC] |
| Capturing Local Context in Transport Appraisal: Case Studies | n/a | May 2021 | New (in response to the 2020 Green Book review) |
| The Proportionate Update Process | n/a | Jan 2014 | New for the restructured TAG, but based on previous TAG unit 1.5 ‘The proportionate update process’ (Jan 2014) |
| Supplementary guidance | |||
| Uncertainty Toolkit | May 2023 | Nov 2023 | — Updated Table 2 on technique selection for a proportionate approach in various situations — Updated advice in para 3.18 on the range of scenarios (breadth of uncertainty) to consider — Updated advice in paras 3.19 to 3.23 (previously 3.19) and 5.52 (previously 5.52 to 5.53) on how and when qualitative analysis should be performed, and on deciding which scenarios are critical to decision-making [Was an Oct 2023 FC] |
| NTEM sub-models | Nov 2014 | July 2016 | Updated to reflect Tempro 7. |
| Mixed Logit Models | Unit 3.11.5 | Jan 2014 | New for the restructured TAG – was previously unit 3.11.5 |
| Bespoke mode choice models | Unit 3.11.4 | Jan 2014 | New for the restructured TAG – based on previous unit 3.11.4 |
| Land Use / Transport Interaction Models | Unit 3.11.3, June 2005 | Jan 2014 | New for the restructured TAG – based on previous unit 3.11.3 |
| Appraisal of New Modes | n/a | May 2025 | New unit. Presents two methods for addressing the ‘new mode problem’: the own-cost approach (as currently implemented in TUBA) and the alternative mode approach (new). Includes guidance on when to use each of these, and worked examples. |
| Appraisal of New Modes – worked examples spreadsheet | n/a | V1.0 (May 2025) | New spreadsheet, presenting the calculations behind the worked examples in the corresponding guidance |
| Supplementary guidance on landscape [monetisation] | July 2021 | Nov 2024 | Updated in line with Nov 2024 Vale for Money Toolkit. No substantive change to method. [Note: this is technically VfM (not TAG) supplementary guidance, but is included here for completeness as it relates to TAG processes.] |
TAG databooks, worksheets, summary tables and other spreadsheet files
Databooks
| Title | Previous version | Current / forthcoming version | What’s new |
|---|---|---|---|
| TAG Databook | V1.24 (Nov 2024) | V2.01, May 2025 | · Change from 2010 to 2023 prices and values. Default price base year (and value year for single-year tables) updated accordingly · Annual Parameters updated with latest ONS and OBC economic and demographic outturn and forecast data · A1.2.1 (cost inflation) updated with latest ONS construction output prices index (COPI) (if available in time) · A1.3.1 (VoTs per person) corrected to update using the appraisal growth rate (flat 1.5%) not the modelling growth rate (GDPpc) · Updates to road vehicle operating cost data: · A1.3.7 (fuel and electricity prices and components) updated to add non-variable costs (NVCs) series · A1.3.8 (fuel/energy consumption parameters) updated with latest EV energy consumption parameters · A1.3.9 (fleet mix forecasts) updated A1.3.10 · (fuel efficiency forecasts) updated · A3.5d and A3.5e (road non-exhaust PM10 emissions factors) updated · A3.4.2 (carbon values and traded prices) updated with Dec 2024 DESNZ traded price projections · New A5.2.1 with carbon price assumptions for aviation emissions under CORSIA · A5.3.1 (operating costs and rail fare forecasting) updated with latest OBS and OBR economic outturn and forecast data · A5.4.2 (MECs) updated to reflect latest economic parameters, fuel prices, fleet assumptions and GHG guidance [Note: V2.0 was published as an FC but did not go live] |
| Common Analytical Scenarios (CAS) Databook | V1.2 (Nov 2023) | V1.3 (May 2025) | Change from 2010 to 2023 prices and values |
Economic impact workbooks and dataset
| Title | Previous version | Current / forthcoming version | What’s new |
|---|---|---|---|
| Functional urban regions lookup workbook | Nov 2019 (webpage says May 2020) | Moved to an MSOA-based (2011 data) approach using similar method to before. Also supplied map in sheet within workbook. | |
| Valuing dependent development workbook | May 2019 | ||
| Wider impacts dataset | July 2021 (v3.3) See also ‘what’s new’ | V4.2 (Feb 2025) | · Updated to reflect latest ONS and OBR data · Public sector added to the sectoral employment data [Was an April 2024 FC] Substantive update was in v4 (30 May 2024). Subsequent corrected versions were v4.1 (24 Sept 2024) and the current v4.2 (Feb 2025)] The public sector was added to the sectoral employment data in the May 2024 version for possible later use (April 2024 FC); this was activated from Nov 2024 (Oct 2024 FC). |
Environmental impacts worksheets / workbooks
| Title | Previous version | Current / forthcoming version | What’s new |
|---|---|---|---|
| Air quality valuation workbook | Nov 2024 | May 2025 | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) |
| Local air quality workbook | Jan 2014 | May 2019 | Changed PM10 to PM2.5 to align with Defra guidance on concentration-based measurement |
| Biodiversity worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| Greenhouse gases workbook | Nov 2024 | May 2025 | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) |
| Historic environment worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| Landscape worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| Townscape worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| Landscape monetisation workbook | Nov 2024 | May 2025 | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) [Nov 2024 and April 2025 FCs] |
| Noise workbook | Nov 2024 | May 2025 | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) |
| Noise workbook – aviation | Nov 2024 | May 2025 | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) |
| Water environment worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
AMAT
| Title | Previous version | Current/ forthcoming version | What’s new |
|---|---|---|---|
| Active Mode Appraisal Toolkit (AMAT) | 2.12 (Nov 2024) | May 2025 * | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) * due soon. FC version still available |
| AMAT User Guide | May 2022 | Optimism bias guidance aligned with unit A1.2 |
Social and distributional impacts (SDI) worksheets
| Title | Previous version | Current / forthcoming version | What’s new |
|---|---|---|---|
| Journey quality worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| Physical activity (basic) worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| Security worksheet [SIs – see also DI security worksheet] | 17 Oct 2013 | Jan 2014 | Definitive release |
| Severance worksheet [SIs – see also DI severance worksheet] | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI Appraisal Screening Proforma | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI accidents worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI air quality worksheet | Jan 2014 | Aug 2014 | Correction – noise replaced with air quality |
| DI appraisal matrix worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI noise worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI security worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI severance worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI strategic accessibility worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI user benefits worksheet | 17 Oct 2013 | Jan 2014 | Definitive release |
| DI output summary worksheet | Not recorded | July 2013 | Release of restructured guidance |
Summary tables
| Title | Previous version | Current / forthcoming versions | What’s new |
|---|---|---|---|
| Appraisal Summary Table (AST) | Jan 2014 | May 2023 | Cell added to indicate which scenario it refers to. [Was an April 2023 FC] |
| AMCB Table | 17 Oct 2013 | Jan 2014 | Definitive release |
| Public Accounts (PA) Table | Jan 2014 | May 2025 | Note on price and value base year updated from 2010 to 2023. (No substantive change to format) |
| TEE Table | 17 March 2014 | May 2025 | Note on price and value base year updated from 2010 to 2023. (No substantive change to format) |
| Carbon Summary Table | n/a | V1.0 (Nov 2023) | New table |
Other spreadsheet files
| Title | Previous version | Current / forthcoming version | What’s new |
|---|---|---|---|
| Cost proforma | Nov 2024 | 17 April 2025 | · Updated price and discount base year to 2023 · Updated parameters reflecting Databook v2.01 (May 2025) |
| Appraisal Specification Summary Table (ASST) | 17 Oct 2013 | Jan 2014 | Definitive release |
| Optimism bias workbook | Undated (published May 2021) | Undated (published Nov 2023) | Labelling corrected [Was not previously an FC] |
TAG software tools
| Title | Previous version / date | Current / forthcoming version | What’s new |
|---|---|---|---|
| TEMPRO (Trip End Model Presentation Program) | 8.1 (Jan 2023) | 8.1 (Sept 2023) | Addition of traffic growth data, enabling the ‘Traffic growth from the NTM’ function. See release notes. |
| DIADEM (Dynamic Integrated Assessment and Demand Modelling) | 7.0 (May 2020) | 7.0.1 (Nov 2022) | Updated user manual (no change to software functionality since v7.0) |
| COBALT (Cost and Benefit to Accidents – Light Touch) | v2.7 (June 2024) | v2.8 (Dec 2024) | · Updated to reflect Databook v1.24 (Nov 2024). · Additional parameters template in 2023 prices to [Was Oct 2024 and Nov 2024 FCs] |
| May 2025 (due soon) | Reflecting Databook v2.01 (May 2025) | ||
| TUBA (Transport Users Benefit Appraisal) | 1.9.17 (Dec 2021) | 1.9.23 (June 2024) | Changes to the treatment of traded carbon emissions, for consistency with TAG databook v1.23 (May 2024). Note: there were no TUBA versions 1.9.18 to 1.19.20 |
| 1.10 (May 2025) (due soon) | · Reflecting Databook v2.01 (May 2025) · Introduction of non-variable costs for appraisal of energy consumption | ||
| TUBA economics files | May 2024 | Nov 2024 | Updated to reflect Databook v1.24 (Nov 2024) [Was an Oct 2024 FC] |
| May 2025 (due soon) | Reflecting Databook v2.01 (May 2025) | ||
| WITA (Wider Impacts in Transport Appraisal) | V2.3 (Jan 2023) | V2.4 (Feb 2025) | Reflecting updated TAG units A2.2 and A2.4 (Nov 2024) and v4.2 of Wider Impacts Dataset (Feb 2025). Updates to user manual. See release notes. |
| WITA economics file | Nov 2023 | with v2.4 (Feb 2025) | Reflecting Databook v1.24 (Nov 2024) |
| May 2025 (due soon) | Reflecting Databook v2.01 (May 2025) |
For the active mode appraisal toolkit (AMAT), see the AMAT table above.