UN investigates how to hit the brakes on traffic pollution


While efforts are being made to tackle air pollution and bring in tougher emissions rules for vehicles, one area remains largely unregulated: pollution from brakes.

For the past two years, a group of experts at the UN Economic Commission for Europe (UNECE) has been working to develop a global methodology to measure the tiny, and potentially toxic, particulate matter (PM) from brake wear.

“Brake wear PM emissions are produced from the friction between the brake pads and the brake disc, which creates small airborne particles that can be harmful for human health when breathed in,” François Cuenot, secretary of the UNECE’s Working Party on Pollution and Energy who met this week in Geneva for its 82nd session, told Geneva Solutions.

Why we are talking about this. Outdoor air pollution accounts for some 4.2 million deaths every year, according to the World Health Organisation. Road traffic emissions, whether from greenhouse gases or particulate matter, are major contributors to this, particularly in densely populated areas.

What's more, particle pollution can also influence the atmosphere's heating and cooling processes, though its impact on climate change is still unclear.

As regulations for vehicle exhaust emissions have become tougher, non-exhaust emissions are quickly becoming the dominant source of traffic-related pollution, according to a report from the Organisation for Economic Cooperation and Development (OECD).

The document, published in December, also warns that the problem will continue to worsen as urban passenger travel demand is expected to double by 2050. With over one billion cars travelling the streets today, the challenge is enormous.

What about electric cars? Unfortunately for Tesla devotees, battery-powered vehicles can emit as much PM as the ones powered by petrol, in some cases even more, according to the OECD's report.

On one side, their regenerative braking system, which reduces speed by slowing down the engine to recharge the battery without the need to hit the brakes, does reduce brake emissions. On the other, battery engines tend to weigh more, an important factor that increases PM emissions from brake, tyre and road wear.

“With the foreseen growth in market share of electric and hybrid vehicles, this trend [levels of non-exhaust PM emissions] will only increase in coming years,” the UNECE stated in its press release, adding that these new technologies such as regenerative braking and advanced driver-assistance will have to be taken into account for developing a global measurement procedure.

Though a pressing matter, rolling out regulations will take some time. The Working Party on Pollution and Energy is hoping to discuss a final measurement procedure by mid-2022 so that it can then be adopted by the World Forum for Harmonization of Vehicle Regulations. Reduction targets and regulations will come later.