Update Optimism Bias Guidance
Edinburgh Tram Inquiry · Edinburgh Tram Inquiry Report · Issued 19 September 2023 · Addressed to: Scottish Government
Government responseScottish Government: Noted (Nov 2023)
DeliveryNo statement from Scottish Government found
Recommendation, verbatim from the inquiry
●Inquiry recommendation, Chapter 25 Recommendation 8 (paragraph 25.220)
The existing Guidance on optimism bias was based on empirical data available almost two decades ago and should be revised to take into account the additional data that is now available. In particular, the reference classes should be updated to include a specific reference to light rail projects and the recommended uplifts for the different reference classes should be adjusted to reflect the additional empirical data that is now available. Thereafter the Guidance should be reviewed and revised to take account of additional data on a regular basis at intervals of not more than five years.
Edinburgh Tram Inquiry, Edinburgh Tram Inquiry Report · 19 Sep 2023 Source PDF →
Published evidence summary
AI-generated evidence summary
In November 2023, Màiri McAllan, Cabinet Secretary for Transport, Net Zero and Just Transition, stated to the Scottish Parliament that the administration follows detailed guidance on procurement, risk, and optimism bias enshrined in the Treasury's Green Book, the Scottish Public Finance Manual, and the Client Guide to Construction Projects (Màiri McAllan response, Nov 2023). The record holds no update since the Scottish Government's response of November 2023 (Màiri McAllan response, Nov 2023).
Sources
AI-generated summary of the record on this page, checked by a second model and automatic checks, 26 Sep 2026.
Government response
●Scottish Government · Noted · 2 Nov 2023
Furthermore, we follow detailed Government guidance on procurement, risk and optimism bias as enshrined in the Treasury’s Green Book, the Scottish Government’s Client Guide to Construction Projects and the Scottish Public Finance Manual. Indeed, the identification and management of risk and adherence to best practice on business case production and assessment rests at the heart of project and programme delivery within Transport Scotland and the wider Government.
Response document: Edinburgh Tram Inquiry Report: Transport Secretary statement
Delivery
No statement on delivery from Scottish Government has been found in the sources searched. This is separate from the response above.
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