Measurement Systems and Characterization of Brake Wear Particles: A Literature Review

Since PM 10 air pollution from braking systems was recognized, the number of studies carried out to measure brake wear particle emissions has steadily increased, especially in the last ten years. To understand the origin of these brake particle emissions, researchers developed their own measuring benches equipped with measuring devices to characterize brake wear particles in number, mass, size, shape and chemically. Test benches adapted for the measurement of brake particles are very different from one study to another, in particular before the publication of the test procedure (UN GTR No.24) that will be used to homologate light-duty vehicles when the future environmental emission standard (Euro 7) is implemented in November 2026. This literary review has two objectives. The first is to describe the systems of measurement (test benches and measuring devices) used by the different authors to characterize brake wear particles and to compare them with the layout described by UN GTR No.24. The second objective is to give the characteristics of the brake wear particle emissions measured by the researchers (PM 10 emission factors, size, shape and chemical composition of the particles).