Talk:Non-exhaust emissions

Brake pad wear, Road surface materials, Tire/Tyre rubber statistics

"Brake wear gets released into the air as particulate matter averaging 12-17 milligrams per vehicle per kilometer".

I quickly read the source and I couldn't find this statement there (David Beddows et at). I tried doing a search of the 30 page document for these figures and key words like "brakes" without success – I couldn't find any breakdowns of the figures for the categories of brake pads, tyres/tires and road surfaces. It might be there somewhere, but I couldn't find it.

The Beddows is about comparison of internal combustion engine vehicles (ICEVs) with (heavier) electric vehicles (BEVs), and if the data comes from here, there is no sign of what category of vehicles are being discussed. 12-17mg/km for a vehicle which drives 20,000km/year would mean approximately 175 grams of brake pad wear per year: I'm not even convinced that an "average" vehicle has 175 grams of usable brake pad material (although large trucks probably would), even without considering that a percentage of brake dust adheres to the wheels.

What kind of vehicle(s) are being referred to? This seems to me far more than what a typical car would do, although there may be some kind of statistical "averaging" of heavy vehicles incorporated (but without saying how - is this traffic on a local main road(s)? Motorway/Freeway/Highway? Residential street? Averaged by vehicle registrations in a particular region?)

What I suggest for improvement:

1. The statements in this paragraph should be accompanied by a more precise reference (page number and/or line number), and the body text should include who found these figures.
2. The statements should be expanded to included what vehicles produce this, and under what conditions.
3. The statements should indicate what they mean by "average vehicle", and how they determined it. Is this an ICEV passenger car? Some mixture of ICEVs, BEVs, passenger cars, buses and heavy vehicles in a particular type of road according to a formula?
4. If the statements are incorrect or inaccurate, they should be replaced with more accurate figures.

The figures I've found on the internet:

• a Japanese study, Hagino et al (2016), which gets figures from one to three orders of magnitude lower:

"The tests were performed using two passenger cars and one middle-class truck. The observed airborne brake wear particle emissions ranged from 0.04 to 1.4 mg/km/vehicle for PM10 (particles up to 10 μm (in size), and from 0.04 to 1.2 mg/km/vehicle for PM2.5. The proportion of brake wear debris emitted as airborne brake wear particles was 2–21% of the mass of wear." https://www.sciencedirect.com/science/article/pii/S135223101630125X

• Garg et al (1998):

"Brakes were tested on a brake dynamometer under four wear conditions. On average, 35% of the brake pad mass loss was emitted as airborne PM. The observed wear rates correspond to vehicle emission rates of 5.1−14.1 mg/mi. On average, 86 and 63% of the airborne PM was smaller than 10 μm in diameter (PM10) or 2.5 μm in diameter (PM2.5), respectively." https://www.researchgate.net/publication/231277179_Brake_Wear_Particulate_Matter_Emissions

However, as these studies was done using brake systems not attached to a vehicle, even this study doesn't appear to take into account brake dust which adheres to the wheels and other parts of the vehicle.

• Liu et al (2022) which tested a brake system with a 139mm out diameter disc, which seems to be that of a small car:

"The simulated PM10 emissions were quite consistent with the measured ones, with an overall relative error of 9%, indicating that the proposed simulation approach is promising to predict brake wear PM10 during the WLTP-B cycle. The simulated and experimental PM10 emission factors during the WLTP-B cycle were 6.4 mg km−1 veh−1 and 7.0 mg km−1 veh−1, respectively" https://www.sciencedirect.com/science/article/pii/S0959652622018820

Fh1 (talk) 23:16, 7 March 2023 (UTC)