27. The representative from OICA introduced ECE/TRANS/WP.29/GRPE/2021/15, exempting modern vehicle from opacity tests. The representative from EC highlighted the need to update the reference K value used, with particulate filter removal remaining undetected due to high this reference value. The representatives from Switzerland and from CITA agreed that the existing 0.5 reference value was no longer adequate and that a much lower value would be desirable. The representative from EC suggested a reference K value of around 0.05 could be a good compromise to improve the failure/tampering detection levels.

28. GRPE agreed to keep discussing a more appropriate K value during forthcoming GRPE sessions, and invited participants to submit proposals on this matter.

29. GRPE adopted ECE/TRANS/WP.29/GRPE/2021/15 and requested the secretariat to submit it to WP.29 and AC.1 for consideration and vote at their November 2021 sessions as draft Supplement 7 to the 03 series of amendments to UN Regulation No. 24 (Visible pollutants, measurement of power of C.I. engines (Diesel smoke)).