38. The Chair of IWG on Particle Measurement Programme (PMP) presented a status report on activities on exhaust and non-exhaust particle emissions (GRPE-79-13).

39. The representative from India enquired about any correlation between existing evaporation tubes and strippers for sub-23 nm particulate emission measurements. The Chair of IWG on PMP answered evaporation was working for diesel engines, and that for spark ignition engines (e.g. 2-stroke L-category vehicles), some artefacts were measured. IWG on PMP was considering adoption of two approaches for the future. The representative from India asked further explanations about the dispersion found in the round robin tests. The Chair of IWG on PMP explained two Condensation Particle Counters (CPCs) were connected to the same exhaust line, one to measure 23nm particulates, one to measure 10nm particulates. He highlighted the location of the sampling points are of high importance and could explain part of the dispersion found. He emphasized that the hot start variability was higher as absolute values were lower than for cold starts. The representative from India finally asked whether the dispersion was fit for post Euro 6 measurements. The Chair of IWG on PMP answered that only one CPC would be prescribed in the future legislation, ensuring more consistent measurement and easier location of the sampling point in the exhaust line.

40. The Chair requested about the expected timeline to deliver on a procedure for sub-23 nm particulate measurement. The Chair of IWG on PMP confirmed they are expecting a working document for the GRPE session of June 2020.

41. The representative of the United States of America confirmed the findings on non-exhaust particulate in the US were consistent with IWG on PMP and the results shown by the representative of the Russian Federation in GRPE-79-07. He explained that the characteristics of tyres are changing to improve safety and rolling resistance and encouraged GRPE to carefully consider the impact of such tyre modifications on the wear of tyres and associated particulate emissions. He proposed to potentially make a presentation at the next GRPE session in January 2020 about the on-going activities in the United States of America on the matter.

42. The Chair of IWG on PMP introduced the revised ToRs of IWG on PMP (GRPE-79-14) seeking to extend the activities of IWG on PMP until June 2021. The Chair of IWG on WLTP asked whether IWG on WLTP should anticipate some work loads to adapt UN GTR No. 15 to sub-23nm requirements. The Chair of IWG on PMP did not expect in-depth modifications to UN GTR No.15 and would be happy to further work with IWG on WLTP to better coordinate the activities.

43. The representative from OICA requested further considerations on transitional provisions when the new method to measure sub-23nm particulates had been finalized. The Chair agreed such considerations were important and will be undertaken when the new procedure became available and ready to be included into legal texts.