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The following is the first of three articles by Carlos Agudelo posted on The Brake Academy about another aspect of dealing with brake emissions as the world – and industry – come to grasp with this challenge.
Five things the industry has done already to address brake emissions
Brakes wear, depending on their specific gravity, can become either airborne or deposited on the road. Irrespective of the amount, the fate, and the health effects of brake emissions, the industry and regulatory entities worldwide have taken proactive and preventive measures to lessen brake emissions. These are ten areas or activities where the industry, government agencies, and research institutes have developed active measures or projects on particulate matter emitted during braking. Some activities have already increased the scientific and engineering understanding of such a complex aspect of the transportation industry.
“All happy families are alike, but every unhappy family is unhappy in its own way,” Leo Tolstoy, Anna Karenina, 1878
All low-emitting brakes are alike (like low operating temperatures, well-balanced brake distribution, low wear friction couples, safe driving habits, strict quality controls in manufacturing, low brake drag, and stable coefficient of friction). Different reasons—sometimes independent and sometimes colluding, can generate brake emissions at much higher rates (such as unbalanced brake force distribution, poor brake cooling, non-technical brake jobs, vehicles with out-of-service conditions, aggressive driving or vehicle overloading, partial formulation designs, lack of repeatable and stable manufacturing and assembly, or unintended effects from failures from other components). These are some of the nuances which keep environmental and health professionals, friction designers, and applications engineers up at night.
The last ten years have seen a surge in efforts from multiple stakeholders that, when put together, provide a clearer image of the path the industry is following to reduce harmful environmental and health effects from everyday driving. Something which was not as obvious ten years ago, when brake dust was mainly a cosmetic concern. The list is not exhaustive, and there are many areas where other sectors like rail transport, or individual companies like those developing on-vehicle capturing devices, testing systems, and vendors of measurement instruments, are making significant progress.
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1. Develop the WLTP-Brake cycle within the European Commission
As of 2019, the European Commission published the Worldwide harmonized Light vehicle Test Procedure (GRPE 81-12) to represent the average driving profile in a 4.5-hour driving cycle (6-8 total run time) using data from over 750 000 km of data collected in different regions. The dynamometer cycle includes ten trips, 303 braking events, and 192 km of driving distance with city, suburban, and highway driving. The development took multiple iterations of vehicle testing at the Lommel proving ground, and the brake cooling method used input from in-vehicle testing in the United States by California Air Resources Board, CARB. This work’s inception was in 2014 when the European Commission established the Informal Working Group. The IWG was given the charter to work towards the” […] development of a set of recommended measurement techniques and sampling procedures, the investigation of typical driving patterns, the compilation and monitoring of on-going research projects, as well as the networking and exchange of information with experts in the field of non-exhaust traffic related particle emissions […]”. The current work of the IWG includes four task forces (1) driving cycle, (2) laboratory method, (3) interlaboratory studies, and (4) regenerative braking systems.
The article can be viewed in its entirety by clicking HERE.
