DfT TAG Unit 3.1 - May 2024 Update
For the eagled eyed traffic modellers amongst us, you will already know that DfT have released an update to TAG Unit 3.1, which came into effect at the end of May 2024.
However, for those of you not aware (and in particular, those who specialise in microsimulation modelling), the update brings some welcome news in the form of a new appendix dedicated to microsimulation modelling.
The latest guidelines can be found at the following link:
https://www.gov.uk/government/publications/webtag-tag-unit-m3-1-highway-assignment-modelling
In addition to the introductory and design sections, which set out key information to contemplate when considering microsimulation model choice, extents, purpose, level of detail and stakeholder engagement requirements, there are also sections dedicated to:
· Calibration – definition, criteria, techniques, and data requirements
· Validation – definition, criteria and techniques, and data requirements
· Convergence – definition and techniques
· Base Model Reporting
The appendix also includes specifics for Forecasting and Future Year modelling, with further details provided on the derivation of flow forecasts, considerations towards model changes and the need for appropriate future year reporting.
Finally, there is a section on Model Quality & Fitness for Purpose, which encourages the adoption of good modelling practices and standards through transparent modelling, suitably defined outcomes, acknowledgment of all risks. The need for independent review is also highlighted, with a collaborative and pragmatic mindset the key for expanding the industry’s knowledge and best practice techniques.
Modelling Group are proud to have worked with the project team (notably Hugh Livingstone and Tom Van Vuren), contributing to writing and editing the microsimulation appendix, taking account of advice and feedback from DfT, National Highways, and Transport for London. There has long been a need for guidance on microsimulation at a national level and the inclusion of this appendix is a welcome addition to DfT’s wider modelling guidance provision.