Study suggests that fresh asphalt is a significant source of air pollution | Hacker News Reader

Study suggests that fresh asphalt is a significant source of air pollution

sciencemag.org

266 pointsdigital55177 comments

Here is the Yale press release: https://news.yale.edu/2020/09/02/asphalt-adds-air-pollution-...

And the paper: https://advances.sciencemag.org/content/6/36/eabb9785

I'd also like to point out that road wear is approximately proportional to the cube (^3) of the weight per axle on a vehicle, so cars are probably responsible for a minority of this pollution.

*edit: some are pointing out that the relevant road wear is proportional to the 4th power of vehicle weight, see the comments below for details.

> I'd also like to point out that road wear is approximately proportional to the cube (^3) of the weight per axle on a vehicle, so cars are probably responsible for a minority of this pollution.

Could you clarify that a bit? Do you mean that the friction of the tires on the road releases nasty emissions?

No, heavy trucks wear out the road significantly more than cars and result in asphalt having to be replaced more frequently.

This is another case where the gas tax isn't really adequate for funding road issues due to the disproportional increase in costs to the increase in fuel usage by trucks. All of the light vehicle drivers subsidize the heavy trucks in all mileage/fuel based tax schemes.

For this reason, in northern latitudes, weight limits for trucks drop significantly during the spring season. Shipping water bottles, ice salt and windshield washer in stores becomes a real pain in the ass.

For what it’s worth, you can buy windshield washer concentrate online. In months where the temperature gets cold, though, you want the alcohol based stuff that won’t freeze and burst a line.

Sounds like we need to expand our rail capacity. Our current rail freight capacity is near 100%.

Why not tax each mode of transportation proportionately to their true cost, and let the market decide?

How do you price in the fact that heavy trucks destroy the road faster, causing them to be replaced more often, causing more pollution?

In other words, how do you price in the pollution? And do you really want to?

Yes, you really do want to. It would be lovely if we could charge proportional to the externalities.

As for how... beats me. Best we can do is rough approximation, and accept that we will continually find out we were wrong and have to adjust the cost structure.

We could get the approximations quite wrong and still get massive economic improvements from where we currently are!

However the challenge isn't the approximations, but the political difficulties. Even taxing based on mileage would cause an uproar. And taxing large pickups proportional to their economic toll on infrastructure would probably start a violent revolution.

Large pickups aren’t an appreciable part of the problem here - 18 wheelers are.

There are a lot of smaller roads where 18 wheelers never travel, and where a 2x weight increase means 10x the road wear (between the cube and fourth power of weight, according to simple models in this thread).

Charge the asphalt companies a carbon tax, and let municipalities create road taxes based on vehicle weight/usage to pay for the extra costs created for road maintenance

The how is difficult -- studies like this are part. "Do you really want to?" is a clear yes. It's called a Pigovian tax, and it's the most unambiguously "correct" way to tax things: you tax things in accordance to their harm to third-parties (and subsidize things in accordance to their benefits to third-parties).

Markets only work if we internalize the externalities, which can most efficiently be done through taxation. Pollution is one of the standard examples of an externality.

Because there is no "true cost" and it's all subjective.

You can ratchet up the tax on heavy trucks because "muh road wear" but then you'll have a world where everything is delivered in small trucks and there will be problems with that. At the end of the day it comes down to a subjective question of which problems get which priority.

or transportation of goods like food become more expensive so people rely on their local farmers instead of getting avacados shipped in from the moon

If you do anything to a low level of the economy (e.g. fuel or energy prices) to the point where consumption at the upper levels is reduced then you're also screwing the poors hard enough that you are either going to get voted out of office or shot in short order (depending on how your system of government handles power transitions).

I agree, but none of this is remotely just or fair without a minimum wage that is a living wage. And what that is needs to be reassessed if policies change the cost of living.

that's life - frank sinatra

Good thing it's something totally within our power to change. - Probably Also Frank Sinatra

>You can ratchet up the tax on heavy trucks because "muh road wear" but then you'll have a world where everything is delivered in small trucks and there will be problems with that

Is that really a bad thing? If shipping via big trucks (compared to small trucks) causes $200 more road wear per year, but saves $100/yr in gas (and other expenses), why shouldn't we use small trucks?

> At the end of the day it comes down to a subjective question of which problems get which priority.

You're right, there will be some subjectivity involved, but at least the general goal is trying to be as neutral as possible. It's not unlike cap & trade for dealing with climate change - letting the market decide what's the most cost effective way.

Small trucks may cut enough emissions by reducing road-wear. If everyone switched from large trucks to an even larger amount of small trucks it's possible the problem is made worse.

Why the focus on small trucks as if they're a panacea?

>If everyone switched from large trucks to an even larger amount of small trucks it's possible the problem is made worse.

Right, but isn't the whole premise that the damage is the truck's weight cubed (or ^4)? Splitting large trucks to small trucks only increase wear linearly.

>Why the focus on small trucks as if they're a panacea?

I'm not. It's a hypothetical.

>it's all subjective.

Let's dream for a moment where the tort system worked perfectly. All environmental externalities would be perfectly priced by class actions. Cause $100,000 of lung damage, pay $100,000 to the survivors. If only such efficient courts existed...

> then you'll have a world where everything is delivered in small trucks and there will be problems with that

So then tax those problems until taxes represent the true societal cost of things

Rail networks have massive network effects. Might be best to let the market not have that one. What with the huge risk of regulatory capture and all.

Looking at e.g. the UK, having some mixed public-private rail system doesn't seem to work that well.

The most efficient freight railways in the world are probably in the USA, and passengers in Japan. Both private vertically integrated things, with the one company owning both rails and trains. But yeah, massive potential for problems as well.

I don't really have a good solution. I'd guess the best industry structure is just "it depends", nothing that is superior to other ways of doing it in all circumstances..

I sort of wonder if private train companies in the US would achieve the sort of interconnection we have in Tokyo. The train station nearest to my house is owned by one company, but after going East two stops the stations and rails are all owned by another company. The station that's part of both of these companies' lines is also a major transfer station to a major line owned by a third company.

As a user of transit I mostly don't have to care about this, but I ended up calling three companies when I lost something on the way home.

This was sort of figured out during the massive railroad booms in the US throughout the 1800s. You can let the market have parts of it but you need guardrails so you don't have some asshole that owns a bridge holding everything up for a city: https://en.wikipedia.org/wiki/Livingston_Avenue_Bridge#Histo...

Motor carriers operate with tight margins and require a heavy regulatory hand. There are multiple overlapping jurisdictions, etc. Law of averages make fuel tax work, but there are holes... if you buy fuel in Delaware, less revenue comes to Pennsylvania, etc.

Shitty operators will do anything to save a buck -- trucks with no brakes operating overweight will travel at night to avoid enforcement based on knowledge of enforcement. Others will find holes in enforcement to avoid penalties -- shady trucks operating in Manhattan will be registered in places where unpaid New York tickets won't impact their registration, for example.

https://en.wikipedia.org/wiki/International_Fuel_Tax_Agreeme...

If you have a commercial vehicle you are supposed to be tracking how many miles you travel in each jurisdiction and how much fuel you buy in each jurisdiction.

I'm sure the "flag of convenience" states that operate cut-rate truck registrations are very diligent in auditing compliance. </s>

Don't y'all have these amazing rivers that aren't really used any more for transportation? Maybe you should couple that up with rail transport :-)

Barge traffic on rivers has been and still is a thing. Maintaining the rivers isn't cheap or easy, of course.

I know the comment was tongue in cheek, but the area in question (Los Angeles) doesn't have navigable rivers. In fact, the Los Angeles river is better paved (lined with cement for various reasons) than some roads in the area.

And as a sibling comment points out, where the US does have good rivers/lakes, notably the Mississippi-Missouri-Ohio network and the Great Lakes, they are used extensively for transport. The only one I can think of that is disused is the Hudson and canals that connect to the Great Lakes.

But the same is true for Europe: larger rivers allow larger, more efficient ships and are still used for transport, and the canal system is too narrow and so mostly recreational now.

You can always (sometimes at large cost) dig wider and deeper canals, or make existing ones wider and deeper. https://www.britannica.com/technology/canal-waterway/Major-i... has plenty of examples of recently dug or now large canals supporting large ships.

How solid is rail transportation in California?

For freight? It's pretty solid.

In calendar year 2019, the alameda corridor [1] processed about 4.8 million twenty foot equivilent units (TEU) [2] and the ports of los angeles and long beach processed about 9.3 million [3]. So around about half of the container trips to or from the port are by rail rather than truck. Some of the containers may just get put on trucks at the rail yards at the other end of the corridor to avoid trucking congestion in the port, but I don't think there's a lot of that. (I could be wrong)

For passengers? It's pretty iffy outside of commuter rail, Amtrak operates on freight lines, and is deprioritized, and there's a lot of freight volume, so there's a lot of delays for passengers.

I don't know the right keywords to find data for the ports of Oakland and Stockton. They probably have a decent rail volume too, but they have more challenging geography to get east than in southern california.

[1] the rails between the port of la/long beach and major rail yards exiting los angeles

[2] http://www.acta.org/pdf/Monthly_TEUREV_History.pdf

[3] https://kentico.portoflosangeles.org/getmedia/a43d3038-7713-...

The way you frame this makes it seem like a road tax is in our future. That, in turn, makes me more skeptical about this study, the funds for which were granted by the EPA. I’m not really insinuating the EPA is after your tax dollars, but the fact that a government agency funds a study that can have tax implications should at least raise an eyebrow. I don‘t know how common this is.

The problem I have with this is that the gas tax was [Edit: this is apparently not true, as was pointed out below] created because exhaust fumes were damaging the environment and reducing air quality - and I agree with that. But now that we have made significant strides towards reducing emissions - both in the way of more efficient vehicles and battery-operated vehicles - causing a decrease in gas tax dollars flowing in, suddenly we have another source of emissions which would require another tax.

I can’t help but feel that at least on some level this will be a money grab - even if the underlying study is confirmed long-term.

>the gas tax was created because exhaust fumes were damaging the environment and reducing air quality

Do you have a source for this? Everything I have read states that gas taxes were first enacted to finance road construction (thereby leading to more exhaust fumes), and gas taxes in place today often dedicate the majority if not all of their funds to road building.

https://en.wikipedia.org/wiki/Fuel_taxes_in_the_United_State...

Actually, I don’t have a source, it was just my assumption, so you’re probably right.

But seeing the downvotes roll in, I should have known better than to question the financial motivation for an environmental study on HN.

Pairing those questions with skepticism of government certainly didn't help.

I think the downvotes are about the misinformation, not the questioning!

I would also point out that gas taxes do not fully fund road infrastructure, and typically cover only about half the cost, meaning that road infrastructure is heavily subsidized by other taxes. (Which if course should be the case for infrastructure, but a lot of car advocates mistakenly believe that they are pulling their own weight with gas taxes.)

Thanks for the info. I’ve updated my original post to point out I was mistaken in my assumption.

As an aside, I treasure the moments when I get downvoted in HN; it's good to at least be thinking differently enough to cause a negative reaction a small amount of the time, IMHO.

You could get a decent approximation of the right tax by taxing diesel more. Especially after dieselgate, there are hardly any light vehicles that use it.

Except in Europe, where Diesel peaked at almost 50% of all vehicles sold - pre dieselgate.

That same hammer would also hamper innovation in new light diesel vehicles. All three auto makers now make diesel half ton trucks and Jeep is expanding it into more vehicles. We should encourage that.

A few things came to mind for me:

- Many of these emissions are described as being from paving, so more frequent repaving caused by increased wear would aggravate the issue.

- These issues seem to be related to temperature, and I suspect that the increased wear by heavier vehicles is largely caused by increased friction (which would increase temperature-related emissions).

- Cracks and potholes expose more asphalt, and are largely caused by the heavier vehicles.

Tires wearing out is indeed a source of pollution though. That material wears off onto the roads.

I thought it was roughly to the 4th power of the vehicle? At least that's what this chart [1] suggests and I've heard in a few engineering podcasts

[1] https://streets.mn/2016/07/07/chart-of-the-day-vehicle-weigh...

It's a complicated function that behaves like different powers at different depths.

But superficial wear (this study) should have a higher power than deep wear (your link). Civil engineers normally used the 3rd power for deep wear...

Maybe the people on your link got a table from something different than what they though it was.

Vehicle weight is not directly proportional to axle count - a 9 axle semi with trailer can weigh 80,000 lbs or 9000 lbs/axle, a 2-axle car weighs 3500 or 1750 lbs/axle. Alternatively, multiplying axle count by 4.5 increases vehicle weight by 25x - so the two can both be true at the same time, the power just changes whether you use vehicle weight or axle load.

What effect does tire width have? Very narrow (<165mm) tires vs dual tires of trucks for example. Smaller area of friction versus lower pressure

>What effect does tire width have?

probably quite an effect, but reducing damage via width will also decrease vehicle efficiency and increase rolling resistance, so the gains at the road may be lost in an overall loss of efficiency at the vehicle, not to mention manufacturing and materials cost, when finagling the tire-width variable.

I don't have any numbers, though.

> will also decrease vehicle efficiency and increase rolling resistance

Not necessarily; one could formulate the tread rubber for such wider tires so they're less grippy per square cm of tread contact-surface, and so exactly as grippy as before per fully-loaded tire. Basically making every change in the opposite direction from what dragster tires do (other than the width.)

That's for peak power. Efficiency is lost in the deformation bending and returning of the walls of each tire as it rolls. i.e. A really highly loaded tire needs to be really well pressurized to prevent overheating and failure due to the losses.

Got a link to engineering podcasts?

>I'd also like to point out that road wear is approximately proportional to the cube (^3) of the weight per axle on a vehicle, so cars are probably responsible for a minority of this pollution.

This is a very, very, large over-simplification and contains some large assumptions about road material, the road base, the ground pressure of the axles and the local climate (which affects the road construction techniques).

This is a rule of thumb to help city planners come up with a ballpark number that's within an order of magnitude. Don't present it as though it's a hard and fast rule.

Hence the caveat “approximately proportional”

Even if it's a ballpark figure, the GP's statement would still be correct, no?

As someone who had to study civil engineering as an undergrad a lot of the formula are empirical. 3rd power law might not coorelate with degradation of some road some road while others might exhibit 5th power law. However if I recall correctly the correlation between road wear and axle load was ^4.

The press release doesn't say anything at all about road wear, pressure or friction, so cars vs. trucks has nothing to do with it.

It appears to be entirely about the role of asphalt releasing compounds when exposed to sunlight and high temperatures.

So even if there was zero traffic on the roads, asphalt would still be producing the described pollution on a bright summer day.

The greatest amount of semivolatile organic compounds escaped when the pavement was heated to 140°C

Asphalt is usually delivered at 275-300f (135-150°C) and needs to be over 185f (85°C) when applied. So, a warm summer day is cold by comparison. Resurfacing is also heavily impacted by use.

It does look like emissions are highest when the asphalt is fresh, even though they persist after that, so to the extent that more wear results in more frequent replacement (and so, more time during which the asphalt is fresh), there's probably some connection there?

Road wear is what makes communities repave roads, so cars vs. trucks has quite a bit to do with it.

Yes, each car does little damage compared to a truck or bus. But how do the numbers compare for the total number of cars vs HTV right now? Is the ratio of cars:HTV better or worse than 1:3?

Uh, why 1:3? European cars are generally about 4x lighter than European TIRs. If the proportions are similar in the US, you should be asking about 1:64 if the cube is right, or 1:256 if the fourth power is.

Edit: also, there's the duration of use per day. Typically about 1h for cars and 10h for trucks here, so you should be asking about 1:2560.

Could this problem be temporarily mediated by expanding the width of tires to increase the surface area and disperse the weight?

Any cyclist and most road workers I expect are saying, “no shit, Sherlock” right about now. That stuff reeks. It’s awful. And we lay it a mile at a time.

And it lingers for a really long time.

In suburban neighborhoods it's common for folks to repave their driveway from time to time.

You can usually still smell it for 4-5 days after it's been applied. Anyone who walks down your block will notice it.

Yeah, have to wonder how this wasn't already completely obvious.

I mean, sure, it's great that it's got an official science stamp on it, but really big duh here.

People have terrible intuition about this kind of stuff. Just look at the number of people installing wood burners for evidence of that.

The problem is that there isn't much of an alternative.

Municipalities have limited funds for roads. And the roads need to be of a certain quality standard, usually set at levels above the municipality. Safety, speed, cost, etc. all must be factored in.

Concrete will do the job, but it's expensive, takes time, and is climate variable. You could use dirt, but then safety and speed are lessened. Wood is possible, but it'll need to be replaced a lot. Gravel is also used, but then road capacity is diminished.

Asphalt is in a bit of a sweet spot in terms of many variables.

Grady of Practical Engineering on YT has a good series on roads here: https://www.youtube.com/watch?v=PIK6I6Q58Ec&list=PLTZM4MrZKf...

In the interests of full disclosure:

Your butt and hands are never happier than when you are on a fresh stretch of newly minded asphalt. It's like silk sheets. If you're riding into a crosswind, the smell isn't so bad and the overall effect is quite pleasant.

But a tail or head wind on a hot day? Man alive.

Maybe we have too many roads to be sustainable, for several meanings of that word.

Concrete can be pulverized and used in new concrete. A fact I might have learned from another PE video (or maybe veritasium).

All asphalt is recycled as well. You don't even have to crush it, you just heat it up and it turns plastic again.

Except the part that is added to new asphalt is where the emissions are, especially the toxic ones. The carbon footprint of concrete is exceptionally high. I don't know where recycled asphalt falls on the spectrum.

Many (most?) of the streets around Dallas are concrete, so it can be done on large scale. Maybe materials are just cheaper there, but it appears to be a viable alternative at least in a warm climate.

There is an alternative, less roads. Make things denser, make it so people don't have to travel as far, and you won't need to lay so much new asphalt.

For some reason most of my peer group think the coming age of remote work is a great excuse to concrete over the rural parts of my country.

Wouldn't it be the opposite? Less commuting means less roads are needed.

> Concrete will do the job, but it's expensive,

But it also requires way less maintenance than asphalt, doesn't it?

As a cyclist, I biked on a fresh (poured yesterday) uphill asphalt section around 1pm today. I put my face mask back on, that was a relief.

Asphalt is a oil based product. Its pretty nasty. Mixed with rocks and you get pavement. There was some talk about classifying it as a hazardous waste especially when then grind the top surface off roads when repaving. It does work well as a durable driving surface.

https://en.wikipedia.org/wiki/Asphalt

An underlooked quality of Asphalt is that it is the most recycled material on earth. Asphalt can be, and generally is, made of old asphalt.

That’s interesting. I wonder what goes into reusing old asphalt (i.e. what new chemicals need to be added/removed in order to make old asphalt pliable or whatever the term is to lay it again).

It isn't just the asphalt that is recycled but many other products are recycled into it as well, shingles, tires, and even glass, can all end up into it.

what they take off the road can be ground and used on site for a layer but mostly its carted off and ground to the same size as the original aggregate and combined into new. since the binding material is still present it reduces the need for more oil byproducts

Super interesting. I always assumed it was a gigantic use of oil globally. Sounds like it doesn’t have to be.

But most of those items are oil originated. At what point can we make asphalt without any new oil?

The term describing this is: RAP (Recycled Asphalt Pavement).

https://www.fhwa.dot.gov/publications/research/infrastructur...

That sounds great for the environment - let’s grind and hide this pile of trash for a few decades, what could go wrong.

I'm sure it goes through some cleaning but generally just heating it up makes it pliable again.

Heat, probably.

Generally it's crushed and a percentage of the final mix uses the recycled crushed asphalt. The quality of the asphalt is lower with higher amounts of recycled materials so high traffic roadways like highways may use 30% recycled asphalt. While lower traffic roadways or things like bicycle paths can use a higher percentage with new binder in the mix.

Recycling asphalt takes mostly heat. You lose some of it on the process, so you must add some new asphalt, and the new asphalt doesn't have the same composition of the original one (but is still asphalt, or asphalt components).

Milled and Crushed, heated, some new aggregates mixed in, new oil, good to go.

You can look up mobile asphalt batch plants if youre interested

There is an interesting video about this on practical engineering:

https://www.youtube.com/watch?v=XKFaC5RYbEM

This was the topic (in part) and title of a Practical Engineering video just last month.[0]

[0]: https://youtu.be/XKFaC5RYbEM

Including the fact that asphalt is generally mixed with tire rubber, therefore recycling old tires. Plastic is now also being added to asphalt to recycle when constructing roadways.

I wonder where that recycled rubber goes as the road surface wears away...

It probably joins all the rubber coming off the tires, settling on or near the road and then washing into the waterways.

In the air as particulate pollution and then it's washed into the waterways.

Do the plastics get released during degradation or do they make up a more tightly bound part of the mixture?

Yes. It was a while ago, but I was linked to something describing how asphalt leeches chemicals into the surroundings.

Uh, yeah. They use recycled tires in astroturf installations as well and there was an epidemic of soccer goalies getting some rare form of cancer due to diving in the "dirt" and getting exposed to the chemicals in it.

Google Amy Griffin or read this https://www.ehhi.org/turf-cancer-stats.php

An Indian scientist named Rajagopalan Vasudevan developed and patented this process. It reduces the bitumen used and improves the quality of flexible pavements, resistace to wear and tear. I think this is a brilliant way to use some of the plastic waste. Also the patent is royality free.

https://en.m.wikipedia.org/wiki/Plastic_roads

This is brilliant. Asphalt mostly consists of polycyclics. Maltenes make up the continuous phase, and are typically alkane-modified resins. Compared to plastics, these are much shorter chains. They are also prone to UV degradation which causes brittlement, leading to road degradation.

Asphalt is just nasty stuff. I'd love to see it get replaced with alkanes (polyethlene and polypropylene from plastic, polyisoprene from rubber)

They are rebuilding a concrete highway next to my house.

A thing I thought was really interesting is that they broke up the old concrete (which surprising to me had no rebar in it), and then ran it through a rock crusher and used all that rock to build up the road bed and I assume also used as aggregate in the new concrete they put down.

I thought that was neat because I've read a bunch of places that old concrete isn't really ever re-used for anything.

Here in Seattle, when they took down the viaduct along the waterfront, they also decommissioned a tunnel that the viaduct connected to. The decommissioning consisted of leaving the tunnel intact and filling it with ground up concrete from the viaduct.

Having worked in road construction, I can say that the amount of diesel fuel that gets sprayed all over the thing during rolling/compaction is abject. At least in Canada, if you spill a liter of anything on the ground you're supposed to file paperwork, contain it, maybe have the environment crew inspect it... Meanwhile they send 5 labourers with no education and 100 liters of diesel fuel to spray all over the ground.

Why is diesel sprayed on the ground?

I may not be explaining this well... But it's very effective at dissolving or softening asphalt, and so it's used to compact the material and finish it into a smooth surface for final rolling/compaction.

I'll preface by saying I'm not trying to downplay cars or the roads.. but doesn't almost everything we consume make pollution in a non-negligible quantity? e.g. when cars are manufactured, the plastics we use, livestock, etc. It's a multifaceted problem that won't be fixed by changing one thing like cars or the roads.

All money spent causes pollution if you trace it back far enough. As a first approximation, environmental impact is directly proportional to cost.

That’s an oversimplification, if nothing else because you can spend money to save money. Likewise you can make a monetary expenditure to prevent other more environmentally costly expenditures.

It's not a bad approximation. More flights, bigger houses, bigger cars, more toys, faster computers. They all cost more and all have a bigger environmental impact. There are a few things where spending will decrease your emissions, loft insulation, possibly replacing your petrol car with an EV, definitely replacing it with an e-bike.

Even if there are savings made what do people do with their reduced energy costs? Mostly buy more products/services.

To some extent yes, but that is different from the claim, which is about "all money."

But also, you're neglecting things like cheaper parts tending to be worse for the environment. Comparatively expensive wood, for instance, would likely cause fewer problems than cheaper plastics. Plus, that's true by virtue of the cheaper parts breaking sooner and needing to be replaced. It's certainly not a universal that luxury goods are eco-friendly, but it is true that eco-friendliness is a factor that requires a premium to be paid for it.

I don't think that's necessarily a very good or helpful approximation. It's very cheap to send vaste chemicals into the sea. It's more expensive to capture them -- and while it might pollute to build a good capture system, it'll _very_ quickly be outweighed by not sending the stuff into the sea.

Due to the lack of externalities being reflected in the cost of fossil fuels, I don’t think that is true.

Environmental impact due to fossil fuels is proportional to energy consumed, which is probably roughly proportional to mass times distance traveled.

I’m sure there’s lots of different types of environmental impact not priced in such as excess heat caused by paved surfaces, air pollution caused by particulates from tires and brakes and fuel exhaust, water table pollution caused by waste seeping down through the earth, etc.

==It's a multifaceted problem that won't be fixed by changing one thing like cars or the roads.==

I don't see anybody suggesting it would. On the other hand, we can't know the negative impact until we study it. Once we study something, we can add it to the list, and stack rank based on cost-benefit.

I think this is some sort of falacy. Everything pollutes, but substituting something polluting a lot, with something polluting half as much, can make a big difference. There are lots of gains to be had in the amount things pollute.

I see this come up really frequently when talking about environmental impact "We can't replace X with Y because Y has negative environmental impacts!"

Never mind the fact that Y might be a lot better for the environment than X in the long run.

A good example of this is hydro power. Yes, concrete emits a lot of CO2. Yes, dams negatively impact fish. Yes, rotting dam algae emit CO2.

But you know what? None of that matters, because dams emit far less CO2 than comparable coal plants and, as a bonus, dams work really well with solar/wind because they can ramp with demand. They are basically giant batteries that self fill.

Nuclear falls well within the same bucket of "Yes, it has negative impacts, those are far less than global warming".

For example, nuclear powered shipping would be a huge positive for the environment. Bunker fuel is one of the worst things we spew into the atmosphere.

I feel this is a really deep problem in our society that is a core contributing factor to all sorts of problems. We can’t build major public works projects, can’t build enough housing, can’t execute on anti-pandemic measures. Any big public endeavor is mired in veto points where any issue, no matter how minor compared to the upsides, can lead to delays or total failure of the project. It seems like only private companies can get anything done. It’s good that somebody is able to get things done, but it would be better if that somebody had a charter to act in the public’s interest first.

To add a confounding factor, the public's best interests aren't generally private entities best interest.

They know this and lobby/advertise/etc to get public opinion and officials on their side.

There's plenty examples of this. For example, early on when nuclear came out fossil fuel companies spent a LOT of money spreading FUD about nuclear. Much of that still exists today.

https://en.wikipedia.org/wiki/Anti-nuclear_movement

Those forms of pollution are concentrated in areas where people aren't living in large amounts.

This form is right next to every house and apartment complex and much worse in cities where large amounts of people live.

Much worse in certain cities which have huge road networks, high car dependence, and no cobblestone to speak of. LA comes to mind. Rome does not. (to pick two extremes)

Local air pollution is a problem somewhat orthogonal to general carbon emissions/ecosystem damage that're far from where humans live. Both problems are important, but there's nothing wrong with recognizing that they're different harms. Reducing local air pollution is still a worthwhile goal to discuss without having to take on the task of making the entire modern economy less polluting. (For a historical example, consider the removal of leaded gasoline/paint)

We should trust our noses a lot more. If it smells awful it's probably polluting!

Paraphrasing a home brewer on the topic of how/why we've had alcohol for so long:

We carry a chemical testing laboratory around with us everywhere - our noses - and it can detect all the ways beer can go wrong and become harmful.

We made it, we could tell by smell if it was going to kill us, so we kept making it.

Sometime later horrible odors became a hallmark of Progress, and has been paying dividends ever since.

I used to live rurally but then moved to the city. It is always shocking noticing all the pollutant smells when I return to the city from a stint in the fresh air of the countryside. It's surprising how quickly your body adapts and begins to ignore the pollution. I know it is around me now but I can't smell it.

Of course, this isn't always accurate, since sometimes things that smell good are not great either: https://en.wikipedia.org/wiki/Benzene. But it's often a good first guess.

Yea I've heard people say they like the smell of gas but I don't. It has a too sharp or burny scent.

Pareto principle in action - remove the bulk of tailpipe particulate emissions, and the previously negligible other particulates take a larger share.

In typical ICE scenario tailpipe accounts only for a half of particulate emissions, another half comes from from brake, tyre and road wear.

http://publications.jrc.ec.europa.eu/repository/bitstream/JR...

Yes, that's true now. I wonder if it was true in 2000 for instance or 1990? Probably not in 1980.

Which reminds me of a video of Cody's Lab, where he refines precious metals out of roadside dust: https://youtu.be/v5GPWJPLcHg

It's a failure of priorities that I see a lot at work and push back on.

The need to act is based on the magnitude of the problem relative to your desired outcome, not relative to the current state of affairs. If you don't do this at the beginning, then 'new' things will pop onto the list as you go along, resulting in solutions that are anywhere from suboptimal to maladaptive.

Looked at holistically, you might notice that 3, 5, 7 and 8 all have the same root cause, and taken together they may be the 1st or 2nd largest problem. They may also be easier to fix.

But no, we're gonna start at the top and work our way down until people get tired of hearing from us.

Also, tire particulates are a large contributing factor to air pollution, much worse than what comes out of the tailpipe.

https://www.tiretechnologyinternational.com/news/regulations...

Tire particulates are worse than _exhaust particulates_, not necessarily emissions, an important distinction. CO and CO2 are not counted as particulates.

Not to forget NOx emissions from diesel motors.

I don't think you understand what they are measuring here. There are a lot of interest groups dedicated to selling oil until there is no more oil to sell, and they have no interest in being transparent about what they mean when they say that tires are worse than internal combustion.

It's pretty clear that the authors are redefining pollution pretty extraordinarily to justify their claims. Only "particulate" counts as pollution, and the lifetime of that particulate, both chemically, and the airborne lifetime, is not even considered. Probably by this measure, the dominant source of pollution on earth is the winds from Africa depositing silt in the Amazon basin.

Lucky they found a use for the toxic waste from oil refineries by mixing it with sand and gravel and rolling it down on roads.

On the other hand, as vehicles go electric, there won't be any new asphalt to make roads for them to run on.

It definitely seems rail might be lower polluting in this respect.

i wonder about the brake dust in not only cars but trains as well. maybe where trains don't decelerate much there is less pollution?

I'm not sure, but I think modern trains usually use electrical braking instead of friction.

Perhaps an all-electric train could, do they just feed it back into the grid? Freight trains mostly use air brakes, which are friction.

A diesel-electric freight train locomotive can use dynamic braking by dumping the electrical energy into a bank of resistors (known as rheostatic braking, opposed to regenerative braking, but collectively called dynamic braking.) However apparently this form of braking is only a small portion of braking that freight trains do since only driven axels can participate in it and most freight cars are unpowered. I didn't consider that.

As far as I know only rarely, and even those trains do have mechanical brakes too. Modern electric locomotives can do engine braking, but brake power needs to be applied everywhere on the train, so most of the train brakes mechanically. (And if you want to engine brake, the energy still needs to go somewhere - so you have additional complexity of feeding it back into the grid or you are limited by how much energy you can dump to heat)

Only (mostly high-speed) passenger trains with driven wheels everywhere can brake well only electrically for non-emergencies. Some also have additional eddy-current brakes that interact with the rails.

For the German high-speed trains they try to design the speed profiles so that they have to waste as little energy as possible by using the motors as generators and feeding it back to the grid. But they still have and use eddy-current and mechanical brakes too. (You can tell the difference if they are delayed: they brake later and more aggressively to make up time. And a full-on emergency stop is loud and smelly.)

This was part of the design behind the N700 bullet trains of Japan. They have motors in all trains in order to distribute weight and thus braking and acceleration ability evenly across the whole train. It reduces wear on all wheels and components but as you mentioned adds complexity in the overall aparatus. They brake at stations using mechanical brakes though if I am not mistaken, the sound is pretty hard to ignore!

At least for freight trains and normal passenger trains (especially diesel), that's probably true.

High speed trains usually use induction brakes (regenerative braking) and as such, they don't produce nearly as much brake dust. Also, freight trains generally don't need to brake very often, since the tracks are free for kilometers to come most of the time.

In general, trains are of course far from emission-free, but as they can transport way more passengers/freight the emissions per person / tonne of freight are still lower than cars or trucks.

Electrified rail also gives the promise of eventually being low emissions when we switch to greener power plant. So it benefits from scale economics twice right now, and will seamlessly switch to entirely green when the power plants do.

That's true.

In Germany, Deutsche Bahn boasts that its electric long-distance trains are 100% powered by renewable energy. There are some asterisks to that, but it's still a great thing.

So yes, electrifying lines really has many advantages: * it allows for high-speed trains * it enables trains equipped with regenerative braking * its trains are driving more efficiently (most diesel locomotives actually are diesel-electric, meaning they have a diesel generator powering an electric drivetrain) * it allows the trains to be powered by renewable energy

All these points drive the overall carbon footprint down in one way or another.

Plus I would think that they're quieter?

MUCH quieter. I occasionally use a diesel commuter train; shockingly noisy compared to the usual electrics.

Friction braking of a steel wheel on a steel rail produces fewer particles (more ductile) which have a higher density (iron > carbon), so the accumulated air pollution should be much less.

For those really curious about details of asphalt concrete construction on California state highways, check out Section 39 of the Caltrans specifications: https://dot.ca.gov/programs/design/ccs-standard-plans-and-st...

These specifications end up being used by a lot of cities and counties in California as well.

> Concrete creates greenhouse gas

I guess its time to also shame walkers and sidewalk bikers

The biggest con that we’ve bought as a society is the push towards personal responsibility in carbon emissions rather than addressing the bigger sources in large ships, energy production, materials manufacturing, etc.

Those bigger sources are created to serve the personal needs. glaring eg. Industrial animal farming

> But this building block of modern civilization may eventually suck some of that carbon dioxide (CO2) back up—enough to cancel nearly a quarter of the gases released making cement, according to a new study.

If you click into the article, it actually contradicts the title. Another click-bait example.

Hot asphalt/bitumen is heated petroleum product.

Is there any petroleum product that is not unhealthy when you heat it up? Gasoline, kerosene ethylene, propylene, butene.... I can't think of anything?

Asphalt driveways start out as very dark black, and then slowly fade to grey. They also start out as very smooth, but as they fade to grey they become more textured.

I wonder if there's a relation?

That applies to any asphalt road.

Basically that's the binding agent (which contains oil) wearing off the surface.

https://www.quora.com/Why-do-roads-turn-grey-when-they-get-p...

Time to start a new company up and invest heavily in it, VC backed, at scale, revolutionizing the industry. Let's call it AsphaltX.

You joke, but there are plenty of VC backed companies trying to revolutionize road surfaces. The most famous are the various companies trying to add solar panels to roads.

Of course Asphalt is pretty awesome on balance, so most of these startups fail spectacularly.

I was actually looking for the comment about the solar roadways in here. I know they are expensive up front, but can lead into charging stations to help offset their cost in the long run (if people are willing to go along with either state run charging stations or privatized roadways). The question is, have there been studies about their environmental impact over X amount of time? I think it was Sweden who put in a length of roadway to test their viability for use.

The idea in principle is solid, most roads are empty most of the time and just sit in the sun. But making a surface durable, keeping the it clean and transparent but also providing good grip in all weather conditions are all hard problems. Solutions to one of them often make the other two worse, and many attempts choose materials that fail spectacularly at all three when tested in the real world.

Maybe we just need to put those solar panels between train tracks, then? Still a lot of unused surface, can use the rails as conductors, easy to clean using a special car.

The downside is that it makes it hard to pour ballast. It also doesn't help at all for road surface (lower their cost or replace "polluting" asphalt).

> can use the rails as conductors

But then bad things happen if you touch them…

Smells so good though.

It's a super cool paper

The roads near my house - https://economictimes.indiatimes.com/videodash.cms?autostart...

Do not click: 30 second unskippable ad.

Link to the same footage on YouTube directly: https://www.youtube.com/watch?v=5NDDncs47ro

This one had a 15-second unskippable ad.

lol

Sorry. I use uBlock Origin.

I had linked to the video frame instead of the article. Clouldn't get direct video link.

Doesnt your link have ads too? Youtube?

Always gets me.. send people a link, with no idea there was ads. The worst was when i sent someone a link to an old tv show, and the page was full or porn ads unbeknownst to me.

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