Development of the Worldwide Harmonized Heavy Duty Brake Cycle (WHBC) for Brake Wear Particle Measurement

While light-duty vehicles already have a test cycle under Global Technical Regulation 24 to characterize brake wear emissions as part of Euro 7, heavy-duty vehicles, also covered by Euro 7, still lack a harmonized test cycle for this purpose. This study presents the development of the Worldwide Harmonized Heavy Duty Brake Cycle (WHBC), a novel test cycle representing real-world HDV braking behavior across urban, rural, and motorway conditions. A large, globally sourced dataset of vehicle activity and existing cycles was analyzed via brake-event extraction and statistical characterization using empirical cumulative distribution functions of key brake metrics. The resulting cycle comprises 246 brake events over 271 km and 5:39 h. An analysis of parasitic losses based on a European heavy-duty CO2 monitoring database indicates that roughly 73% of kinetic energy dissipation must be absorbed by the brakes. Dynamometer testing confirmed the feasibility and repeatability of the cycle as well as providing first insights into particle measurements. The WHBC offers a technically sound, broadly representative basis for the ongoing development of a harmonized regulatory test procedure for heavy-duty brake particle emissions.