Guidance: Transport analysis guidance

Department For Transport

October 13
14:34 2021


This content contains guidance on the conduct of transport studies. The guidance includes or provides links to advice on how to:

  • set objectives and identify problems
  • develop potential solutions
  • create a transport model for the appraisal of the alternative solutions
  • how to conduct an appraisal which meets the departments requirements

Projects or studies that require government approval are expected to make use of this guidance in a manner appropriate for that project or study. For projects or studies that do not require government approval, TAG should serve as a best practice guide.

The department endeavours to keep the guidance up-to-date in light of new evidence and developments in best practice modelling and appraisal methodologies. Changes are released through an orderly release process, giving users early sight of changes and when they are to be released definitively. Users working on longer-term business cases should refer to the proportionate update process when considering incorporating these changes into their analyses.

For users wishing to understand how the new structure relates to previous version of TAG a correspondence table (MS Excel Spreadsheet, 24.7KB) is available. An archived version of the previous TAG site is also available.

TAG update reports

These reports describe our approach to updating TAG in 2020 and 2021.

Forthcoming changes

Agreed alterations to existing TAG, including details of the information being altered and planned dates of release.


This overview provides general introductory 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.

Guidance for the senior responsible officer (SRO)

This guidance is for project promoters and sponsors who manage and oversee those projects as a whole.

It provides knowledge on how the evidence derived from the transport appraisal process can be used to support the transport business case and inform the decision-making process. It introduces the high-level concepts of transport appraisal and modelling, the important outcomes required and the main risks to monitor and manage.

Guidance for the technical project manager (TPM)

This guidance is for technical managers that oversee the detailed modelling and appraisal work.

It provides more detailed knowledge on the key components of the transport appraisal process including options development analyses and appraisal describing how the concepts of transparency and proportionality should be applied. Overall, this should enable those managers to programme and manage the deliverables and resources more effectively. This identifies the main outputs expected in transport business cases and provides checklists of those expectations in more detail.

Transport appraisal process

This guidance gives a more detailed description of the transport appraisal process, including more detail on the 3-stage process of option development, further appraisal and implementation/evaluation.

Transport appraisal case studies

These case studies show how local context can be captured as part of the transport appraisal process, to make the argument for transport investment that supports local economic growth objectives.

Proportionate update process

This guidance provides an overview of the departments process for updating guidance, when guidance is intended to become definitive and how analysts should go about adopting changes to guidance in a proportionate manner.

Guidance for the appraisal practitioner

These guidance documents inform practitioners of best practice in preparing the necessary outputs for the appraisal of transport schemes and policies.

A1 cost-benefit analysis

These guidance documents give advice on the principles of cost-benefit analysis in transport appraisal, the estimation of scheme costs and the calculation of direct impacts on transport users and providers.

A2 economic impacts

These guidance documents give advice on the appraisal of the wider impacts, regeneration impacts, and dependent development impacts, of transport interventions.

A3 environmental impacts

This guidance provides advice on the appraisal of the environmental impacts of transport interventions. It deals with impacts on both the built and natural environment and on people. The environmental impacts covered in this manual are noise, air qu

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