[bigiain]

>They're torn up from the road and rubbed off from the tyres themselves. The majority is obviously coming from the road.

Not sure even that adds up to believable.

The Sydney Harbour Bridge is about 500m long between the pylons. It has "more than 150,000 cars per day" on it (according to the snippet from a google search). If all of that was from the road, that'd mean there's about 160 tons of road getting torn up per year. It looks to be ~30m wide on Google Sat view, and "google first hit" research indicates road base weighs 1.9tons per cubic meter. It's be losing almost 6cm of depth along the whole span every year if all those numbers hold, or 3cm per year if "only half" of that comes from the road and the rest from the tires. They don't resurface it anything like often enough for that to be true...

[mgleason_3]

Let's test it with basic math! The claim is "...performed some initial tyre wear testing. Using a popular family hatchback running on brand new, correctly inflated tyres, we found that the car emitted 5.8 grams per kilometer of particles.

If the average tire lasts 40,000 Kilometers then multiply that by 5.8 grams = 232Kg. 232Kg/4 tire per car = 58Kg per tire of tread. The tread is about 35% of the tire so the tire would need to weigh 165Kg. The average tire weights 20-22Kg, so that's a damn big tire!

New Asphalt might get tour up and account for additional particulate matter, but my understanding is that process slows considerably once the aggregate (small rocks) is exposed.

[TheSpiceIsLife]

Perhaps it’s mostly existing particles laying on the road that are thrown up by the next vehicle’s tyres as it passes?

[bigiain]

That's a pretty long stretch from the claim: "we found that the car emitted 5.8 grams per kilometer of particles".

[JangoSteve]

But is it a long stretch from the claim: "Non-exhaust emissions (NEE) are particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during on-road vehicle usage."

Resuspension of road dust is literally one of the 4 things they defined as the NEE they're measuring.

[bigiain]

OK, I missed that bit.

But counting "resuspended road dust" as "emissions" seems pretty far fetched to me. Especially if that's a significant portion of the "5.8 grams per kilometer of particles", and you then push out a press release with the hyperbolic headline claim "Pollution from tire wear 1000 times worse than exhaust emissions."

And they then have the audacity to claim: "Emissions Analytics seeks to bring transparency to a confused market sector."

Pretty sure I know who's funding them now, without even bothering to google it...

[clouddrover]

Who's funding them? Radical balloonists? Big Rail? Maybe it's the Hovercraft Lobby! I never did trust them.

[bigiain]

Fossil fuel industry.

(But if it _is_ the Hovercraft Lobby, I'm totally in!)

[qtplatypus]

It might be due to different tires. People in Sydney are very unlikely to be driving tires designed for ice and snow.