20. The expert from ETRTO introduced a new design of the C3 Standard Reference Test Tyres (SRTTs) that are used as reference tyres for snow grip and wet adhesion performance (GRBP-78-28-Rev.1). The expert for Japan posed a question. The Chair invited ETRTO to submit a working document for consideration at the next session.

21. The expert of the Informal Working Group on Wet Grip Performance of Tyres in Worn State (IWG WGWT) presented their status report (GRBP-78-16) and draft updated Terms of Reference (GRBP-78-15). GRBP adopted the revised Terms of Reference, as laid down in annex III to the session report.

22. The expert of IWG MU presented analyses of measurement uncertainty made by ETRTO and the experts from the project on Strengthening the Effect of quieter tyres on European Roads (STEER) (GRBP-78-06). The expert from IWG MU also gave an update on the C2 tyres noise temperature correction (GRBP-78-04). GRBP took note of these documents.

23. The expert from IWG MU proposed measures to reduce variability (ECE/TRANS/WP.29/GRBP/2023/19 and GRBP-78-05). GRBP adopted the proposal, as laid down in GRBP-78-05, and requested the secretariat to submit it for consideration and vote at the June 2024 sessions of WP.29 and AC.1 as draft Supplement 2 to the 04 series of amendments to UN Regulation No. 117.

24. The expert from AAPC recalled GRBP-77-23 from the previous GRBP session and presented GRBP-78-33 with modifications to the rolling resistance values for LT-marked tyres. According to him, for reasons of safety and durability, some heavy-duty pickup trucks in a specific geographical region require LT-marked C3 tyres with performance characteristics suited to their use in rough terrains and for industrial/agricultural purposes which result in rolling resistance values higher than specified for C3 tyres in general. Therefore, he proposed to make an exception for such LT-marked C3 tyres in the rolling resistance tables.

25. The experts from France, ETRTO and OICA pointed out the need to study the proposal in more detail. Some experts feared that the requested exception for one region may have global implications. GRBP invited AAPC to liaise with the interested experts with a view to bringing more elements into consideration at the next session.