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Comment by rconti | Hacker News Reader

Unfortunately, brake dust and tire rubber also represents a surprisingly large amount of particulate matter as well. I wish I had the source, but it was far more significant than I ever would have guessed.

(I have an EV, a gasoline powered sports car, and a diesel SUV (with particulate filter and urea injection))

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EV regen braking partially helps with the brake dust, at least. May be counteracted by the tire rubber because EVs can be driven in a more “spirited” way.

Great point.

I also find it humorous that the busybodies who insist that stop signs be installed every block of their neighborhood arterial have to suffer from the resulting air and noise pollution.

I drive 'spiritedly', but I suppose the tire wear due to hard cornering is not nearly offset by the saved brake pad and exhaust emissions!

So you're getting mad at people who are reacting irrationally to you speeding through neighborhoods?

I think there's more than one problem here.

Stop signs are a pretty bad solution for traffic calming, though. The key to effective traffic calming is to shape drivers’ natural behaviors, not authoritatively demand it.

A stop sign that serves no purpose than to slow people down will piss off drivers more than anything, and lead to people speeding between signs or running them. It will make your street noisier as impatient people aggressively obey the signs.

A typical neighborhood would be much better off if traffic was calmed by adding kerb extensions or narrowing the lanes.

I think the above commenter might share my frustration that local politics is often full of people unknowingly demanding the wrong solution to their problem.

The US is gradually coming around (heh) to roundabouts.

I hope so, the only one in my immediate area is about 30 feet in diameter... That's right, there is a single-lane for the roundabout itself!

As someone who lives in a neighborhood full of stop signs (just about every other street is signed), I find that it actually does exactly what you're saying, i.e. shape drivers' natural behaviors.

Almost everyone elects to drive on one of the nearby "thoroughfares" rather than stop and start all the way through the neighborhood. So I see stop signs as the perfect solution.

I'd agree this wouldn't probably work on a road that sees heavy traffic already though.

Except where I live they also put stop signs on the thoroughfares. Some places just have messed up traffic.

Stop signs are not meant to calm traffic, they're safety features. When you have to stop, you're not blindly driving into traffic, that's the whole point. You stop, you need to start driving again, you have the time to look to the left and to the right.

You can look left and right while gently rolling through there is no need to come to a full stop in many cases.

No, you need to come to a full stop at a stop sign. That's why it says STOP on it with capital letters - so that even idiots know what to do.

The point is that other jurisdictions get away with using way fewer stop signs than in North America, while having much safer roads.

Yep, from driving in the States it is clear that they liberally use stop sign where you really want a yield sign.

You can, but few do. The Stop sign makes sure you've come to a halt and are focused on what happens next instead of "just cruising".

Interruptions reset focus (unless you're so distracted that you don't notice the sign).

Congratulations, you just got an immediate fail on your driving exam!

Even with perfect visibility, ignoring stop signs can kill:

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

Slowing down to idle speed and ensuring the intersection is clear absolutely nothing like what’s being addressed in that video.

Nope! I don't speed through neighborhoods; in fact, I drive more slowly than most people through them. I did, however, have a commute through a neighborhood, for 10 years. (There was a 30mph arterial off of which spur roads went into the neighborhoods; no houses fronted the road, just fences).

A number of 4-way stops existed on the route to the office complex for no valid reason whatsoever. The arterial traffic was the vast majority of traffic. I watched over the course of 10 years as more 4-way stops were installed to calm traffic, which is specifically contra-indicated by proper traffic engineering. In fact, I remember reporting on one community meeting, where the community hired a traffic engineer who specifically told them not to use stop signs for traffic calming; they did anyway.

The stop signs actually took away from the attention folks paid to cross streets. Eyes down, stare at stop line, come to a stop, go.. it was much easier to not notice cross traffic or pedestrians!

They all should have been roundabouts, frankly.

Anyway, my point is, 4 way stops are an environmental nightmare in every possible way, and rarely the correct solution.

In retrospect, saying that I drive spiritedly immediately after talking about neighborhoods, was unfortunate juxtaposition on my part. The two are not related!

I moved to the US from the UK, where yield ("give way") signs were the standard and stop signs an attention-getting rarity.

I've often wondered how much harm to health has been done by the increased emissions at excess of stop signs (at least in the parts of the US I've visited). Does it outweigh whatever reduction in accidents you get by forcing a stop at junctions which (to my untrained eye) could safely be controlled with a yield?

I would be surprised if it did. The way a lot of our roads have been designed doesn’t really make yield signs an option. Only recently has the US begun to embrace roundabouts over the basic 90 degree intersection. Unfortunately, it’s hard to retrofit existing intersections because roundabouts take more space.

As you say, roundabouts take up more space, and they are not nice for pedestrians. They're good for major interchanges if you don't want to build an underpass and there's lots of land. If land is cheap though, where are all the cars coming from?

Why aren’t yield signs an option? In Europe they’re ubiquitous, everywhere where a road or street lower in the road hierarchy crosses a higher-tier one. No roundabout needed. As far as I know they work just fine.

In the 90s, many roundabouts were removed especially in the northeast. I don’t think this is true. In New Jersey alone I can remember seven or more very large roundabouts that were removed.

Those that you’re thinking of were likely “rotaries” which have some major design, functional, and qualitative differences as compared to roundabouts. Size, travel speed, and enforeced entry angle are the main differences between rotaries and roundabouts.

And then to confuse matters further “traffic circles” are common as traffic calming devices on the west coast. These are also round, but are very small and do not have a splitter island preceding. They usually sit in the middle of small residential intersections.

Also, sometimes rotaries (the largest, fastest, and most dangerous of the trifecta of round traffic things) are sometimes called traffic circles, which are otherwise the smallest / slowest traffic device.

If all that is confusing, well, you’re not alone. My feeling is that roundabouts and traffic circles are good, but rotaries are just highway interchange supercolliders. Removing them from the northeast was very good.

you missed an important purpose of stop signs which is to make a route less appealing to motorists in the first place. ultimately this is necessary if the volume of traffic is ever to be reduced.

| I drive 'spiritedly'

please don't

> I drive 'spiritedly'

My recommendation is to consider getting into motorcycles (seriously!). People who push things in their car are largely externalizing risk to other people. Motorcycles largely internalize their risk.

You can get an inexpensive motorcycle that will likely thrash any car you’re likely to afford. Plus, the skill required to operate a motorcycle makes it a lot more engaging to ride. Lastly, motorcycling is just far more exhilarating than driving.

I don’t want to shame you for wanting to drive hard, but you can satisfy your desires more fully while reducing the chances of killing or disabling someone who doesn’t have your appetite for risk.

EDIT: I am a motorcyclist, but not a very spirited rider. It turns out riding safely is plenty of excitement for me. I have friends who love to push it however, and I only challenge them to wear better gear and learn more skills.

I'm also a motorcyclist, although I don't own one at the moment and haven't ridden much in the last few years. (and a cyclist, and a runner...)

I also know people who do the periodic track day in their performance cars, and then dial it back on city streets. It's another way to get your thrill on while still minimizing risks to others. It's apparently a blast—I'm not sure I'm ready for it, but I'm sure some day I'll work up the courage.

Yeah, I've got a dozen or so track days under my belt, and have done some car control/teen driver instruction as well.

I no longer feel the need/desire to "go for a spirited drive" on the weekends, or whatever. Part of that is age, part of it experience, I suppose. But I very much enjoy a good run at an on-ramp or particularly nice section of open road from time to time.

There is the problem though that riding a motorcycle makes it a lot more likely you're going to die in a crash (even if it's not your fault).

Teslas are actually pretty bad in this sense, since they are fairly heavy and sporty. My car (a Nissan Leaf) makes me feel bad if I push it too hard (specifically, it has a deeply unsatisfying acceleration curve while in “Eco” mode) and is much lighter, and I think cars like that would be better for this kind of thing.

In the other hand I often do my commute without using the brakes at all, using regen braking only.

> Unfortunately, brake dust and tire rubber also represents a surprisingly large amount of particulate matter as well.

That crap ruins clothes too. I cycle and the stuff that comes off the road is crazy sticky, oily, black and horrible. It doesn’t wash out and is even hard to get off clear coated bike.

Conservation of mass. Fuel turns into CO2, H2O, nitrous oxides and a couple of worse things. Out of that, only H2O isn't a pollutant. Every liter (or every gram) of fuel must fly out of the exhaust as one of these things, otherwise it would accumulate inside the car. Now compare how many liters (grams) of fuel you use per year, versus how many grams of break pads and tires. That figure simply cannot be true, it sounds like a convenient myth circulated by oil industry.

Referencing conservation of mass doesn't make sense. While CO2 is technically a "pollutant", it's not in the same league as the others. Particulates affect air quality in a way that CO2 does not.

The claim isn’t that brakes and tires contribute the most pollutants, but the most particulate pollutants.

Specifically, PM10, hard particles below 10 micrometers. CO2, Nox, etc from a car are hot gasses which expand relatively quickly, so dumping kilograms and kilograms of them is required to raise ambient air measurements above unsafe zones (measured in ppbs usually, see [0] for the EPA standards for NOx, PM, lead, etc).

Particulate matter, being solid, doesn’t spread as quickly as gasses. Small enough particulate emissions can be ingested into the lungs, and from there into the bloodstream. Once there, they can scrape blood vessels, eventually leading to plague and various heart conditions. Very trace amounts of PM10, and specifically smaller PM2.5 that can slip through the lungs easier, can have terrible health outcomes. In the EPA standards I linked, ug/m^3 is roughly equal to ppb, so the standard for PM2.5 is about 1/5 the level of NO2.

ICE engines generally only develop PM10 particles from insufficiently high temp combustion. For modern cars it isn’t absurd to suspect that brakes and tires produce more PM10. Here’s a summary of research done on the matter [1].

If you live in Europe, the US, or Canada, indoor and outdoor PM2.5 emissions will shave a few months off lifespans. China’s lifespans may be cut by as much as 5 years from particulate matter. [2] (not a scholarly source but links to them)

[0] https://www.epa.gov/criteria-air-pollutants/naaqs-table [1] https://publications.jrc.ec.europa.eu/repository/bitstream/J... [2) https://qz.com/1071421/this-is-how-much-of-your-life-air-pol...

> The claim isn’t that brakes and tires contribute the most pollutants, but the most particulate pollutants.

Yes, but that's the "spin", the gaslighting. "Hey, don't look at the huge amount of other pollution our gas vehicles produce, instead look at this small portion where we are not the main villain. Repeat after me: Baaaad break pads, baaad!!" Fossil fuel industry is fighting for their survival. Even if I agree with the numbers and the research, I can't agree that we should focus on this. The greenhouse gases pollution is a much bigger problem, EVs solve that, so if their break pads still produce the same amount of particulates, what does it matter? Don't let them get away with "see those EVs are not as good as you were told".

Focusing on PM pollution tends to reduce CO2 emissions. Most PM 2.5 comes from burning fossil fuels, so insisting on lower levels means burning fewer fossil fuels.

PM studies are able to tie pollution directly to lives and thus dollars (through statistical lives). So, if reducing coal use costs $2.7B a year, but we extend enough lives, prevent asthma, etc., to equal at least $2.7B then as a country we should enact the regulation. The US starting doing exactly this from 1996-2003 and it reduced CO2 emissions by making coal plants, steel mills, etc., more expensive to operate. As a result, PM studies like the Harvard Six Cities study were highly controversial and fossil fuel companies lobbied hard against them. It is a lot harder to tie climate change to direct costs because the impacts are somewhat fuzzy and on a long timeframe.

In this case, discovering brake pads and tires cause PM2.5 means we can invest in less-emitting brake pads. But this isn’t likely to produce tires/brakes that dramatically reduce emissions. A more likely approach is investing in mass transit, which would reduce CO2 output.

I wouldn’t say greenhouse gasses are a larger problem but a rather a harder to coordinate long-term global problem. PM pollution caused 4.2 million premature deaths in 2016 [0]. It is hard to directly state how many deaths climate change caused in 2016 but conservative estimates [1] are for about 500,000 deaths a year by 2050. Most PM deaths stem from terrible industrial air in poorer countries which if combated would also dramatically cut CO2.

[0] https://www.who.int/news-room/fact-sheets/detail/ambient-(ou...

[1] https://www.cnn.com/2019/01/16/health/climate-change-health-...

Don’t forget that EVs use regenerative braking heavily, which generates power instead of brake dust.

They still rely on friction brakes. Especially at low speeds and/or heavy braking, which is what most braking in cities is. Also because of the extra torque a more jerky driving style is possible. I'm really sceptical that current EVs make any real difference to brake and tyre particulates.

Drivers of manual petrol cars can already reduce their brake dust by using engine braking. If one drives very carefully it is possible to not use brakes at all. Indeed it should never be necessary. Any time you hit the brakes means you were going too fast. But how many people drive like this? Barely any. Instead people speed right until the last minute then slam on the brakes. Then as soon as the opportunity arises it's heavy acceleration until the next slam of brakes. Driving EVs like this will produce just as much brake dust.

No, most of EV braking in the cities is regenerative.

When I had an EV, I had rusty brakes even after my commute. That’s how little I used my brakes. I used regeneration braking exclusively except for rare circumstances where something unexpected happened.

Eventually I had to brake on purpose a few times to keep my brake discs shiny, because the rusty discs looked awful

My understanding is that at least where I live most remotely reasonable people use engine braking in city driving almost exclusively. Indeed needless use of the brake pedal is regarded as a sign of a poor driver. But other countries may have different driving cultures…

Not that I've noticed here in Australia. Personally, my current car is an auto, and trying to engine break just isn't very effective without switching to manual in my car. Engine breaking can also be noisier, as may have to shift down gears in a way that means the engine revs relatively high, for a brief time - making it a more noticible noise.

Out in the country, and for me that often means the hills and mountains, then engine breaking is a much bigger part of my driving style, esp down hills!

Engine breaking also doesn't cause your break lights to come on, and they provide a quicker signal that a car is slowing, than relying on people to detect the change in speed.

They still rely on friction brakes. Especially at low speeds and/or heavy braking, which is what most braking in cities is.

I've been driving hybrids for the past five years and in my experience even in heavy traffic friction brakes aren't used nearly as much as in regular ICEs.

There's a constant, thin layer of rust on my rotors that I just can't scratch off in any way short of braking on an off-ramp on a highway.

I imagine EVs, having overall better regenerative braking, rely even less on their rotors.

No.

I've always owned at least one manual transmission vehicle, but the EV does an order of magnitude more regenerative braking than any passenger car internal combustion engine does.

Why 3 cars though? You did your research, you must be aware of the grey energy associated with manufacturing ~5 tons of extremely inefficient transportation vehicles.

They bought those vehicles used perhaps?

Does that change things?

Sounds like because that poster has options they don't have to drive the ice vehicles very often

I'm sure those who want to complain will always find a reason. I'm sure that my purchases and 'hoarding' drove up demand which increases prices and pushes people into newer cars or makes used cars less affordable to the poor, meaning they stick with older less safe, less efficient vehicles, or something.

FWIW, my wife and I carpooled in the EV to and from work, every work day, until covid hit; now I work from home and she drives solo to the hospital.

But again, it probably doesn't matter. The EV is too heavy and the rare earth materials were mined in unfriendly ways, and the weight of the car means it sheds lots of tire material, and not all of our electricity comes from the solar panels on the roof, and we should live closer to work and walk everywhere anyway, and the alcohol I consume has a negative impact on the water supply in a drought state, and....

(don't let anyone find out that sometimes I drive to the racetrack just to go around in circles and end up back where I started!)

You seem to clearly understand what's at stake and yet you still passive-aggressively attack me.

Everything that you said is true, and it should be evident by now that baby steps like a couple of people carpooling in an EV when it's convenient to do so will not cut it. For every couple like you there are 10 couples who don't have the means to purchase an EV and their situation won't change by 2050, when cheap energy (read petrol) will be on the way out.

While it's an honourable thing that you are using your excess hard-earned money to buy EVs and solar panels instead of SUVs and fracking stocks, please understand that you're living above the living standards of most people and not everyone can afford this, and for them, reducing footprint = self-restraint.

Whether used or not, if they own a car that they don't use, another car will be built and put on the market instead, as long as other people need them.

Because I like cars.

A couple of articles on tyre pollution:

https://www.emissionsanalytics.com/news/pollution-tyre-wear-...

https://edition.cnn.com/2020/07/14/world/microplastic-pollut...

I have some very heavy doubts about the validity of their data. Look at their primary findings:

"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."

Most tires seem to be around 7kg, which means according to their data a car would have all 4 tires reduced to nothing after 4828km. With most tires going bald after ~50,000km (not fully vaporized mind you), there's clearly something wrong here.

My guess is they tested brand new tires which may shed particulate quickly at the start, similar to how a new carpet sheds exponentially more at the start.

I think you're right, new tires have a lot of flash and channel runners that are artifacts of the rubber molding process and are she'd very early in the tire's life.

It's also the material on the road being heated and ground up, not just the material from the tyres themselves.

There's more information here:

https://www.ukimediaevents.com/publication/955cc42f/30

They said that all four tires combined lost 1.8kg, which implies they only drove 340km? Also, this is literally based on measuring the weight of the tires apparently, so how much of that became PM2.5 class particles is a mystery.

The article also mentions "track testing", which if used for the test, would easily explain the enormous material lost after a short time. Track racing is very different than highway driving...

Is the rubber oxidizing? Some of the mass might be coming from the air.

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