5. The expert from the Informal Working Group on Measurement Uncertainties (IWG MU) presented their final report (GRBP-79-02) and a draft document for reference (ECE/TRANS/WP.29/GRBP/2024/8 and GRBP-79-48-Rev.1). During an in-depth discussion, several experts from contracting parties expressed concerns about the formal adoption of the document for reference and its legal status. They pointed out that the document could be misinterpreted as being legally binding and modifying the established sound limits in UN Regulation No. 51. In the absence of consensus, GRBP postponed the discussion to the next session.

9. The expert from the Informal Working Group on Measurement Uncertainties (IWG MU) presented a revised document for reference (GRBP-80-07-Rev.1) replacing ECE/TRANS/WP.29/GRBP/2024/8 considered at the previous session. The experts from the Netherlands, Switzerland, United Kingdom and EC expressed concerns over possible misinterpretation of the purpose and content of the document, in particular the suggested 3.5 dB(A) margin and the last sentence in paragraph 1.1.1. In the absence of a consensus, the Chair proposed to keep the document on the agenda of the next session as a working document.