Pollution from tire wear is worse than exhaust emissions?

>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...

That doesn't make sense to me either. Take a busy German highway (as I don't know the average load on US ones), easily 100k cars per day. There are parts of highways which don't get replaced for 20 years easily. Plus apart from tiny fraction of north europe (and maybe Canada?), nobody ever uses studs.

Back of the envelope math tells me 1 km of highway would lose some 730 tonnes of asphalt, per year (so 14,600 tonnes in 20 years). If we talk about normal car wear, this simply isn't happening on those unkempt roads. It would leave huge lanes of deeper surface where asphalt is lacking. There isn't visible wear on lanes that are used mostly by cars like that. Roads have mostly potholes.

What happens on those roads is, sticky asphalt is worn away (but not at the mentioned rate), and what remains are stones which basically don't wear, and tires touch only that. At least highway surface I saw was like that.

What damages roads greatly are trucks, especially overloaded ones (say limit is 15 tonnes, they take 22 tonnes and hope to not be checked... welcome to east european mentality).

> "the danger in the particles comes from their size with smaller particles being more dangerous for humans. And that road particles were something like an order of magnitude larger than exhaust fume particles from diesel engines."

Exactly. It might look bad when you compare the mass of particles, but if you compare the particle counts, it's exhaust emissions that produce the big numbers - of really tiny (sub-PM2.5) particles.

The studs in tyres are small carbide rods, which will easily chew through a soft material like asphalt. A rubber tyre would seem to be quite a bit softer than asphalt in colder conditions, so I have a hard time imagining the rubber wearing the asphalt down so significantly.

Study mentions EU and source company has offices in Stokenchurch, UK and Stuttgart, Germany. I doubt they tested with studded tires and called it typical.

They did test with brand new tires - that's the likely source.

"Emissions Analytics .. [self proclaimed?] leading independent .. specialist for .. measurement of realworld emissions .. performed .. initial tyre wear testing. .. on brand new, correctly inflated tyres .. [and] found that the car emitted 5.8 grams per kilometer of particles."

I have been wearing studded slip on crampons when walking my dog this winter. The ice has been ridiculous, I’ve fallen twice already when not wearing them. Not great for the sidewalks, I know, but the dog needs his walks or he would... get sad

We have not banned diesel engines in Stockholm at all?

If the particles were coming from the road then roads would wear in very visible ways.

But we don't actually see that kind of wear. Roads don't typically have grooves on them where the cars go that are lower than the middle which doesn't have tires driving over it.

I did the calculation in Freedom Units and converted to grams per km. Assuming tires last 60,000 miles or 100,000km and got 0.1 gm/km. So matches your analysis closely.

Notable I put 60,000 miles on my cars tires since I bought it. They are due for replacement kind of whenever.

Perhaps, but that would have to be a pretty steep curve, and one would expect that kind of falloff to have shown up in the data here (unless they literally drove the car once for only 1km, which...would be its own problem for credibility).

Roads are filthy. Cody's Lab once did a video where he collected road dust from the side of a highway, and refined out all the precious metals from it. That's from one small section of highway, just imagine the scale of the pollution across the whole of the states. Concrete dust, rubber, metals, fuel, oil. Cars and car infrastructure is dirty business.

https://www.youtube.com/watch?v=v5GPWJPLcHg

I thought brake pads use asbestos which contribute to the noxious particles.

I do think Vehicle-to-vehicle communications will eventually minimize the all the chicken necking, evening out the traffic and thus less breaking.

I agree. But tires do shed a lot. Consider a brand new tire has grove depth of about 8-10mm, and many drivers change tires when their groves are 0-2mm (yes, some idiots keep driving until they have slicks or "a pop").

Then budget tyres surely wouldn't make a difference?

So it would be better to have a bunch of smaller trucks moving cargo. And that means a lot more work for truck drivers.

> Truck driver. Not quibbling, just adding nuance.

You're absolutely quibbling though.

> So you should include in your calculations that the load is spread out over eighteen tires, as above.

The fourth power rule is specifically about axle load, not about wheel load. It's also an estimate / rule of thumb (which is why it's so useful), not a precision instrument.

But hey if you want more precision than the FPR we can do more precision: https://pavementinteractive.org/reference-desk/design/design...

As the link notes, road engineers usually work in LEF/ESAL (ratio to a standardised 18000lbs axle load), and provides some conversion tables.

Assuming a relatively large 4000lbs sedan this is 2000 lbs per axle, or 2x0.0003 LEF = 0.0006 LEF.

A fully loaded truck would be ~0.3 for the 12000lbs front axle, and 1.11 for each of the rear tandem axles, for a total of 2.52 LEF.

2.52 / 0.0006 = 4200. Which shows that the fourth power rule's 4096 was pretty close but if anything underselling it.

Taxing by fourth power axel weight per mile sounds good

$10 for a bike doing 1000 miles a year, so 1 cent a mile. Gross axel weight about 100lb.

So axel weight of 1000lb would be $100 a mile.

F150 at 2500lb would be $4,000 a mile.

I suggest putting the first year on the sale price, so that $200 bike costs $210, and the $60k f150 costs $60 million.

On the topic of tire wear, I find that my rear bicycle tire will last roughly 3000 miles/4800 kilometers. Even summer performance tires on cars will last about 8000 miles (and most all season tires will go for at least 20,000 miles).

In France the rubber tyre lobby is so strong, the got them on subway cars. No joke: https://en.wikipedia.org/wiki/Rubber-tyred_metro

In January there was this report: Microscopic pieces of plastic have been discovered in the most remote locations, from the depths of the ocean to Arctic ice. Another place that plastic is appearing is inside our bodies. We’re breathing microplastic, eating it and drinking plastic-infused water every day.Plastic does not biodegrade. Instead, it breaks down into smaller pieces, and ultimately ends up everywhere, including in the food chain. Pieces that are less than five millimeters in length, around the size of a sesame seed, are called “microplastics.” https://graphics.reuters.com/ENVIRONMENT-PLASTIC/0100B4TF2MQ...

On Germany the best lobby work to put transportation on truck instead of rail is done by DB, German Railroads, with their freight services. Compared to trucking you can easily double lead times, increase costs per ton and decrease trackability and reliability.

I don't doubt it, we have a local road here that has been fine, but this year they decided to drive a lot of truck loads of snow to save a skiing event from another city up that road and now it's completely destroyed and it needs new pavement and possibly new foundations in several places.

Trucks should really only be a last resort for the last mile to the store and the rest should be sent by rail or boat and loaded onto trucks if necessary.

They also have huge externalities when it comes to damage to other cars, when my car is hit by rocks on the road it is always coming from a truck.

I highly doubt this in cold areas but might be true elsewhere

We have such roads here in NY called parkways, cars only no busses or trucks. Absolute disasters. I frequently take the Belt parkway in NYC to long island via the southern state parkway. That thing looks like it was carpet bombed. They have been patching massive delaminations and joint failures on a weekly basis all winter and we have barely had any freezing weather or snow (it's been spring all winter.) One delam by an interchange was so deep that it took out a few car tires with low side walls.

I was annoyed at these failures and some light reading. You can make more robust roads by making them thicker with a sturdy foundation. Of course this comes at a much higher cost. For example, the autobahn pavement thickness is 27 inches. Whereas by me they mill a few inches off the top of whatever sad situation in below and top it with another 4 inches or so. This is because robust roads are costly and there are so many other things in a muni budget which need attention. So they compromise and lay down a cheap road.

> I'd be interested to know how wear scales with tyre pressure.

Apparently not in any way relevance in face of the fourth power rule, as road authorities worldwide just use the 4th power rule for road wear estimates, without accounting for minor factors (type of axles, axle arrangement, surface contact and suspension systems).

Depends how the axle load changes.

There's no "why", it's a rule of thumb / estimate called the "fourth power rule" (or "fourth power law" but there are other unrelated fourth power laws) established experimentally in the late 50s / early 60s by the AASHO. Basically they built a bunch of roads to the same specifications, drove streams of vehicles through and monitored pavement deterioration.

He was underselling it.

Unless you walked naked out into the woods and built your life entirely from found materials, literally everything in your life was at some point or another hauled by a truck.

Everything.

This is not a hyperbolic way to make an argument, it's the truth. Sometimes you'll have to go pretty far back the chain of events, maybe as far as raw materials, but at some point (probably several) X was on a truck for any X.

A hippie commune that grow all their own food living off the grid? Their clothes, their tools, the paint on their house, it all rode on trucks.

Two-ish years ago truckers in Brazil went on a strike to protest increased gas prices and corruption and it only took three days before the president ordered the military to force the trucks into moving again. That's how hard it hits if trucks stop moving.

The military couldn't do shit though because the trucks hauling the diesel powering the military vehicles were part of the protest so they got nowhere.

If all the trucks stop right this second, we'll be living in post-apocalyptic chaos by Friday. No joke.

Except no. The heaviest Tesla Model 3 weighs 4,100 lbs. The heaviest Ford F-150 (the most popular vehicle in the US) weighs 5,600 lbs.

Not really. EVs are slightly heavy. Loaded trucks are much heavier.

Side point: EVs do most of their breaking via regeneration, so much less brake dust emission.

The battery is heavy but the powertrain is much lighter. You can make light electric vehicles, look at the i3 for example.

Maybe not all the particles come from the tyre?

They could come from the road, or the brakes, or leaves / dust on the road.

Do most people’s tyres last longer than 50k kms? Maybe I’m doing something wrong...

Fall out of the air. Into the sewers. Then into the rivers, and then the sea, where they are broken up into microplastics and return in the food chain.

Working in a tire shop I do get the feeling that the wear is highest when new.

Or surface roads. Once a month I can come out and sweep 2 or 3 cups of dust off my balcony from living next to a road.

We moved a young coworker into a first floor appt in downtown and there was black soot on all the windowsills. I taught him about soap and vinegar and we suggested an air filter and being judicious with opening the windows, or finding a window fan with a prefilter.

It had just not occurred to me that the busses and trucks were pumping out that much soot in the modern era.

You could see it was tiny sticky pieces of rubber.

I think that's mostly a marketing pitch and an outdated one at that. Safety tech has come a very long way.

It is true, but only marginally and mostly at very high speed, heavy impact collisions.

"Basic requirement for modern living" – what an absurd claim to justify a SUV. I wonder how people in most non-US countries even get by, if the basic necessities of life aren’t met. /s

I specifically said "standard use".

It's totally understandable that someone as individual contractor might need a bulky pickup to haul construction materials, and I don't take issue with that.

As for SUVs they will obviously be heavier, sure, but how much more value does a Cadillac Escalade provide at over 5,000 pounds compared to an XT4 that weighs, 1,600lbs less? And then how frequently is that value actually utilized?

Rubbish. Go to South Africa and they're driving around in small hatchbacks. Farmers drive pickups (bakkies), but normally sized ones. There's simply no way those monstrous things are a "basic requirement". You are so out of touch with how most people live.

The rural poor still drive Cavaiers and whatnot. You absolutely "can" drive a Fiesta (or some other compact) if you live somewhere rural. It just is a standard of living below what most people expect in 2020.

People have the money to buy things that they want and makes their lives easier so it's no surprise that they do.

Everything is killing us, but some things faster than others and so we have to prioritize, but hedge. Woodworkers have dust collection systems, air exchangers, and occasionally respirators, so they don’t get something akin to asbestosis from sawdust. What escapes gets processed by soil fungi so not a big problem.

Microplastics have a possibility to do bad things to us over the long run by accumulating in our soils, and playing out like a slow train wreck. I have my fingers crossed that saprophytic fungi are already on the case. But it’d be good if someone gave Paul Stamets a research grant.

The water situation is of more immediate concern, and feels more hopeless to a two-rungs-above-armchair environmentalist like myself.

Can someone substantively reply instead of just downvoting this comment?

Tread wear isn't a measure of quality, it's a measure of the how much 'grip' a tire is designed to have. High performance tires are softer to grip better, but wear out much much faster than tires designed for higher mileage. The higher mileage tires have worse performance characteristics - greater stopping distance, etc.

The $400/corner tires on a sports car usually last about 5-8000 miles. They’re about as high quality as it gets.

At least in the US, we have Uniform Tire Quality Grading [0]. According to Consumer Reports, which tested at least 47 tires, "most tires should live up to their mileage warranty claims"[1].

I've seen "high-quality" tires with a very low treadwear rating and I've seen "low-quality" or "cheap" tires with a very high treadwear rating. But the press release only mentions "high-quality" without defining "quality" at all. Which adds to the dubious nature of the claims.

[0] en.wikipedia.org/wiki/Uniform_Tire_Quality_Grading

[1] https://www.consumerreports.org/cro/magazine/2015/09/the-tru...

they're also measuring vastly more "emissions" over the life of the tire than there is material in the tires, so it appears that what they're actually measuring is the asphalt dust that's being created by the interaction between the road surface and the tire - a longer-wearing tire would presumably be harder material and cause slightly more road wear as a trade-off to less tire wear, so if they had actually tested it a higher-quality tire might cause more of what they're classing as emissions.

but you can't really make an assumption either way when you've only measured on a sample size of one.

5.8 grams per kilometer would mean in only 10,000 KM your tyres lose 58 Kg. Seems way off.

"Smoke" is underselling it a bit. Tyre wear creates PM2.5, which is toxic. I don't consider that outright misleading in comparison to misstating an upper bound as a tight bound.

But 4.5g/km implies 225kg after 50000 km which doesn’t seem possible. Something definitely smells fishy.

Of course higher numbers are worse in an apples-to-apples comparison. The question is whether this is that.

For example, maybe tail pipe emissions make climate change worse, but kicking up dust on the road gives people lung disease.

To look at it the other direction, 5.8 g/km times 75,000 km means they have to somehow produce 435 kg of pollution per set of tires.

Without some more explanation (are they building some kind of model to extrapolate to the entire supply chain?) that seems more than a little implausible. It seems most likely from the context that they are measuring shedding of brand new tires and trying to pass that off as a representative value.

I guess the idea is that it’s a contributor to the acute dose in the car’s immediate vicinity, but without that context it seems like another misleading detail.

Exactly.

Question is, what is the dosing level that would cause harm, and what are the routes that this material takes that might rise to such a level, vs how much is, e.g., stuck on the pavement and washed into the ditch with every rain?

I would run a couple standalone couple hepa aircleaners as well.

I had the same experience, in SF too. Second floor corner apartment on Fell St, a wide and busy road along the park. The windowsills on that side accumulated black dust unlike the other side of the corner.

... because he opened multiple windows and the only one to gather grime was facing the street.

No. When things roll very tiny pieces break off both the rolling thing and the thing rolled over. If we want to travel by rolling (which seems like a yes) along the ground then that's going to produce PM 2.5 air pollution.

Flying is definitely worse, for at least the medium term and perhaps forever, and magnetic levitation is so expensive you're just not going to do it at scale.

The effect from pushing a stroller will be greatly (much more than linearly) smaller than from a goods delivery truck or a railway train, but it's there. We just have to consider this when deciding what's a good idea.

A tire that doesn't wear is a tire that rapidly overheats and loses grip.