In this article, I will revisit the topic of brake dust, in order to update the latest developments in this crucial area, review some timely legislative activity in this area relevant to braking and other vehicle technology areas.

An informative point to start this journey is to look at the inquest into the death of a British girl from asthma-related complications, which recently completed. The coroner concluded that air pollution was a major contributor to the untimely death of this girl, which is the first time such a cause of death has been noted. The coroner also took the rather unusual step of calling on local government ministers to address holes in local legislation, which allow for significant levels of air pollution to continue unchecked, far in excess of WHO guidelines. The coroner was specifically concerned with particulate matter levels, including the smaller PM2.5 class of particles, which easily enter the blood stream through the lungs.

In previous posts, I have covered the significant role of brake dust in particulate matter levels from traffic, and the notable changes in air pollutant levels that resulted from lockdowns at the start of the recent pandemic. In summary, it is clear that traffic contributes to air pollution, and that brake emissions will be the most significant focus of legislative efforts related to traffic in this decade. Exhaust emissions have long been considered the primary source of vehicle emissions, but efforts beginning in the latter half of the last decade have shown a clear path towards severely curtailing or fully eliminating these altogether. Beyond that, brakes and tyres are the primary sources, with brakes being of most importance due to the smaller size of particles compared to tyres.

Legislative work in this area is beginning to bear fruit. The work of the Particulate Measurement Programmefrom the Joint Research Centre of the European Commission has been focused on lab testing installations for brake emissions. The latest published statement includes a timeline to conclude and report on findings within 12 months, effectively creating a reference test regime against which particle limits can be enacted in legislation.

At the same time, Japanese legislators have already defined their own test cycle for brake dust emissions measurement, JASO C470, 2020. This cycle will form the basis of a similar laboratory test in Japanese law, much like the European efforts. A similar level of activity is underway at the California Air Resources Board, who have been focusing on brake dust as the next frontier in vehicle emissions for over half a decade. Once these test regimes are established, the legislators can then set limits on particulate matter from brakes, just as they have been doing for exhaust emissions for decades.

Fig. 1 – Particulate sizes relevant for vehicle emissions

So we can see there is a clear benefit from reducing particulate emissions from a health perspective, and that this benefit is being sought by legislators right across the world. OEMs are certainly not blind to the issue, either. We have seen evidence in the past of devices on test both for passenger cars and urban rail, and we have covered extensive innovation work searching for suitable solutions in past blog posts. Looking at the patent applicants, its’ clear that many OEMs, suppliers and innovators are sharpening their interest in this area. And this interest is also clearly seen within the leading brakes industry conferences around the world, with contributions from academia, service providers and legislators buttressing the efforts of the OEMs and suppliers already mentioned. In particular, the SAE Brake Colloquium will again this year devote a significant portion of the agenda to clean braking topics. And before then, the upcoming Eurobrake conference will have multiple sessions on brake emissions topics, ranging from the legislative outlook, technical approaches, test method development and of course innovative solutions. On Tuesday May 18th, the opening Keynote addressof the conference will come from the UK Department of Transport, reviewing legislative activity for brake emissions. On Wednesday May 19th, two technical sessions will address the macroscopic details of Brake Emissions, with contributions from the legislative teams of the EU, Japan and the CARB, as well as submissions from leading OEMs, Suppliers and Testing experts. (Part 1 and Part 2). On Thursday May 20th, a session on the microscopic details of brake emissions will take place, with a variety of legislators, academics, OEMs and suppliers showing their latest thinking. 

Fig.2 – Terra Dura Brake Encapsulation Device

Throughout the Eurobrake conference, many technical innovations related to brake emissions will be presented. One of the most capable and unique solutions, which promises zero brake emissions, is the Terra Dura system from Advanced Braking Technology.

Terra Dura is a sealed brake system, where the brake disc and calliper are encapsulated in a rugged exterior shell, thereby protecting the brake components from the external environment, as well as protecting the environment from the effects of brake emissions. Advanced Braking Technology have established an enviable reputation in brake technology for mining and off-road working vehicles, where their brake products offer robust state-of-the-art solutions for some of the most challenging work environments on the planet.

Fig. 3 – Typical working environment for mining vehicles

Vehicles with traditional exposed brakes working in such harsh environments often have brake failures within a small number of working days, due to the ingress of foreign objects. While this normally means extensive maintenance and replacements, in some circumstances these failures can lead to more serious outcomes, with damage, injury and in rare cases, fatalities. While it is beyond the scope of this piece to discuss failure mechanisms in detail, it is clear that small silica, metallic or rock particles can attack piston seals, pad surfaces, hose connections as well as the bearings, half shafts, sensors and cables.

By creating sealed solutions, Advanced Braking Technology have been able to offer significant safety and economic benefits for vehicles operating in these types of work environments.

When we consider the issue of brake emissions, a sealed system can offer a comprehensive solution for preventing dust particles from escaping. The Terra Dura system can both protect the brakes from damage in harsh working environments, while protecting natural life in any environment from emissions. Unlike filtration systems, the hermetically sealed casing works equally well for all particle sizes, and allows for safe disposal of wear debris during vehicle service. 

Advanced Braking Technology will make a comprehensive presentation at Eurobrake on Monday 17th May, and further details can be found on their conference page (if you’re registered for the conference), or indeed their website.