54. The Chair of the IWG on PMP presented a status report (GRPE-72-22) on the activities of the group. He reported on the ongoing investigation on the measurement of exhaust particle emissions with a size below twenty-three nanometre and on the calibration of particle number measurement systems. He mentioned that the current PMP equipment specified in Regulation No. 83 could measure the number of particles with a size below twenty-three nanometre by properly changing the counting efficiency of the condensation particle counters, but he underlined the increased uncertainty of the measurements due to the presence of artefacts and particle losses, particularly when measuring particles of a size below ten nanometre. He explained that high dilution ratio helped reducing the artefacts but new technologies such as catalytic strippers would be recommended in this case. He continued his presentation on non-exhaust particle emissions as result of brake wear and the interaction between tyre and road. He explained that the good progress made on assessing particle emissions from brake systems may derive in a proposed test procedure in the future, whereas assessing tyre and road wear particle emissions was much more challenging. He added that it was likely to require more investigation due to the difficulty to separate tyre and road contribution.

55. GRPE noted the intention of the IWG on PMP to submit a summary report on the results of the investigation carried out on non-exhaust particle emissions at the next GRPE session in June 2016. GRPE acknowledged the progress made by the group.