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Scottish Transport Appraisal Guidance (STAG)

Scottish Transport Appraisal Guidance (STAG) consists of two parts:

The Guidance represents best practice in transport appraisal, supported by a Technical Database which provides detailed guidance on the methodology and reporting structure to be used when completing a STAG appraisal.

The communication of future updates, known as Business as Usual updates, will be made available through the Technical Database. The overarching principles as set out in the Guidance remain the same and are not subject to regular updates.

The Guidance supports the Scottish Government’s objectives by providing a clear framework to assess evidence based transport problems and opportunities. It does so by promoting robust, objective-led analysis that can be consistently applied in all transport appraisal contexts.

STAG is one process comprising four phases – Pre-Appraisal, Part 1 Appraisal, Part 2 Appraisal and Post Appraisal – and should be applied proportionally but comprehensively, with the level of detail determined by the scale of the transport challenges under consideration. The principle of being objective-led, rather than solution-led allows the appraisal of options against Planning Objectives, STAG Criteria and establish policy directives, and provides a robust evidence base for decision makers. Any final report must also include proposals for robust monitoring and evaluation plans.

A robust transport appraisal provides evidence to decision makers on transport investement. In Transport Scotland, a transport appraisal undertaken in accordance with guidance can provide the Strategic Business Case for investment. A business case provides the documentation with the reasoning and justification of a scheme. In order to satisfy this, the Office of Government Commerce and HM Treasury have laid out a four stage process that should be followed in the development of business cases. The stages are:

  • Stage 0 - Business planning: Strategic Outline Plan (SOP)
  • Stage 1 - Scoping: Strategic Business Case (SBC)
  • Stage 2 - Planning: Outling Business Case (OBC)
  • Stage 3 - Procurement: Full Business Case (FBC)

STAG guidance should also be referred to when undertaking an Outline Business Case, during which the 'Strategic' case and the 'Socio-Economic' case are revisited.

More details on the development of business cases for Transport Scotland can be found within the following publication, Guidance on the development of business cases in Transport Scotland.

For help and advice on the application of this Guidance, please email the Scot-TAG Mailbox or use the Contact Us link. To receive automatic e-mail notification of updates to Scot-TAG you can register your details with our free newsletter subscription service. Please note, you should select the Scot-TAG Updates option only if you do not wish to receive e-mail alerts on other Transport Scotland news.

Practitioners should note that superseded versions of STAG are available in the Archives.

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