5. The experts from the Informal Working Groups on Measurement Uncertainties (IWG MU) and on Additional Sound Emission Provisions (IWG ASEP), as well as from ISO, presented editorial corrections and clarifications to the 03 series of amendments to UN Regulation No. 51 (ECE/TRANS/WP.29/GRBP/2023/12, GRBP-77-05 and GRBP-77-26). GRBP supported these amendments and noted that they were already included in ECE/TRANS/WP.29/2023/2 that would be considered by WP.29 at its forthcoming session in March 2023.

6. The Chair of IWG MU reported on their activities (GRBP-77-10-Rev.1) and presented amendments to the document of reference on measurement uncertainties (GRBP-77-07 and GRBP-77-08). GRBP adopted the amendments and requested the secretariat to publish the revised document of reference on the GRBP website.

7. The expert from IWG MU introduced a proposal that aimed to amend UN Regulation No. 51 with tables showing the measurement uncertainties when performing type approval, conformity of production (COP) or field testing (e.g. market surveillance) (GRBP-77-09). Some GRBP experts suggested that these tables be included not in the UN Regulation, but in another document, for example, the above document of reference. Following an exchange of views, GRBP decided to revert to this issue at the next session.

8. GRBP recalled that, on 1 July 2023, a one-year monitoring period would start for collecting and analysing test data on the Real Driving Additional Sound Emission Provisions (RD ASEP). The expert from OICA presented their views on the organization of this process (GRBP-77-14) and proposed a draft monitoring data sheet for the purposes of RD ASEP data collection (GRBP-77-15-Rev.1). GRBP noted that the Technical Services, under overall responsibility of the Type Approval Authorities, should play a key role in gathering the required data sets and sending them not less than every three months to an independent contractor selected by OICA, who would check the quality and analyse the data. OICA invited Contracting Parties to inform OICA by the end of February 2023, if they would be willing to financially contribute to the project.

9. To clarify the process of data collection, the experts from Germany and OICA proposed amendments to UN Regulation No. 51 (GRBP-77-13-Rev.1). GRBP adopted the proposal and requested the secretariat to submit it for consideration and vote at the June 2023 sessions of WP.29 and AC.1 as draft Supplement 9 to the 03 series of amendments to UN Regulation No. 51. GRBP also requested the secretariat to publish on the GRBP website, the final version of the monitoring data sheet (currently GRBP-77-15-Rev.1) which would be available in May 2023.

10. GRBP noted that the above amendments, if approved in June 2023, would enter into force around January 2024, while the data collection should start on 1 July 2023. GRBP counted on the cooperation of Contracting Parties and urged Type Approval Authorities and Technical Services to collect and transmit the RD ASEP data as of 1 July 2023. GRBP also invited WP.29, at its June 2023 session, to reiterate this request to Contracting Parties.

11. In view of the forthcoming RD ASEP monitoring, GRBP agreed to resume the activities of IWG ASEP and to extend its mandate until December 2024. At its next session, GRBP decided to review the Terms of Reference of IWG ASEP and invited experts to prepare proposals.

12. The expert from China reported on their research on measurement methods for heavy-duty vehicles in multiple driving mode conditions (GRBP-77-28). The experts from Germany and OICA commented on the study.