TAG uncertainty toolkit
Toolkit for analysing and presenting information on future uncertainty in the transport system.
Documents
Details
A toolkit that provides practical information on:
- the analysis of uncertainty in modelling and appraisal
- techniques for exploring that uncertainty in the context of future travel demand
- how to present this data to decision-makers
- the common analytical scenarios, including narratives and how to apply them proportionately in transport business cases
It supplements TAG Unit M4: forecasting and uncertainty.
A common analytical scenarios databook has also been published.
The previous version of this guidance was released in May 2023.
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
Published 19 May 2021
Last updated 3016 NovemberOctober 2023
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Update history
2025-12-11 10:00
‘TAG uncertainty toolkit’ and ‘TAG uncertainty scenarios: upcoming changes’ updated.
2025-10-16 09:30
Added forthcoming change: updates to TAG uncertainty guidance.
2023-11-30 10:00
TAG uncertainty toolkit updated.
2023-10-19 10:00
Added forthcoming change about appraisal guidance updates.
2023-05-31 10:00
TAG uncertainty toolkit updated.
2023-04-19 09:43
Added forthcoming change: spring 2023 data book and guidance updates.
2022-12-21 15:35
DfT uncertainty toolkit updated.
2022-08-08 09:37
Forthcoming change to guidance note added, giving details of updates to be made in November 2022.
Details
A toolkit that provides practical information on:
- the analysis of uncertainty in modelling and appraisal
- techniques for exploring that uncertainty in the context of future travel demand
- how to present this data to decision-makers
- the common analytical scenarios, including narratives and how to apply them proportionately in transport business cases
It supplements TAG Unit M4: forecasting and uncertainty.
A common analytical scenarios databook has also been published.
The previous version of this guidance was released in May 2023.
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
Published 19 May 2021
Last updated 3016 NovemberOctober 2023
+ show2025
href="#full-history">+ show all updates
-
Update history
2025-12-11 10:00
‘TAG uncertainty toolkit’ and ‘TAG uncertainty scenarios: upcoming changes’ updated.
2025-10-16 09:30
Added forthcoming change: updates to TAG uncertainty guidance.
2023-11-30 10:00
TAG uncertainty toolkit updated.
2023-10-19 10:00
Added forthcoming change about appraisal guidance updates.
2023-05-31 10:00
TAG uncertainty toolkit updated.
2023-04-19 09:43
Added forthcoming change: spring 2023 data book and guidance updates.
2022-12-21 15:35
DfT uncertainty toolkit updated.
2022-08-08 09:37
Forthcoming change to guidance note added, giving details of updates to be made in November 2022.
Details
A toolkit that provides practical information on:
- the analysis of uncertainty in modelling and appraisal
- techniques for exploring that uncertainty in the context of future travel demand
- how to present this data to decision-makers
- the common analytical scenarios, including narratives and how to apply them proportionately in transport business cases
It supplements TAG Unit M4: forecasting and uncertainty.
A common analytical scenarios databook has also been published.
The previous version of this guidance was released in May 2023.
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
Update history
2025-12-11 10:00
‘TAG uncertainty toolkit’ and ‘TAG uncertainty scenarios: upcoming changes’ updated.
2025-10-16 09:30
Added forthcoming change: updates to TAG uncertainty guidance.
2023-11-30 10:00
TAG uncertainty toolkit updated.
2023-10-19 10:00
Added forthcoming change about appraisal guidance updates.
2023-05-31 10:00
TAG uncertainty toolkit updated.
2023-04-19 09:43
Added forthcoming change: spring 2023 data book and guidance updates.
2022-12-21 15:35
DfT uncertainty toolkit updated.
2022-08-08 09:37
Forthcoming change to guidance note added, giving details of updates to be made in November 2022.