
Study suggests that fresh asphalt is a significant source of air pollution - digital55
https://www.sciencemag.org/news/2020/09/it-s-not-just-cars-make-pollution-it-s-roads-they-drive-too
======
nickff
Here is the Yale press release: [https://news.yale.edu/2020/09/02/asphalt-
adds-air-pollution-...](https://news.yale.edu/2020/09/02/asphalt-adds-air-
pollution-especially-hot-sunny-days)

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

~~~
gwbas1c
> 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?

~~~
pathseeker
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.

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

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

~~~
throwaway0a5e
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.

~~~
calvinmorrison
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

~~~
sgc
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.

~~~
calvinmorrison
that's life - frank sinatra

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

------
hinkley
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.

~~~
Balgair
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...](https://www.youtube.com/watch?v=PIK6I6Q58Ec&list=PLTZM4MrZKfW8JLYNhJe2uWNa0eIfent3B)

~~~
noobermin
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.

~~~
rorykoehler
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.

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

------
whalesalad
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.

~~~
save_ferris
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).

~~~
Shivetya
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

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

[https://www.fhwa.dot.gov/publications/research/infrastructur...](https://www.fhwa.dot.gov/publications/research/infrastructure/pavements/11021/11021.pdf)

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epgui
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.

~~~
jiofih
Why is diesel sprayed on the ground?

~~~
epgui
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.

------
EarthIsHome
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.

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

~~~
ironmagma
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.

~~~
tonyedgecombe
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.

~~~
ironmagma
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.

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

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

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

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

~~~
IngvarLynn
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...](http://publications.jrc.ec.europa.eu/repository/bitstream/JRC89231/jrc89231-online%20final%20version%202.pdf)

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

------
iancmceachern
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...](https://www.tiretechnologyinternational.com/news/regulations/pollution-
from-tire-wear-1000-times-worse-than-exhaust-emissions.html)

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

~~~
ehnto
Not to forget NOx emissions from diesel motors.

------
Merrill
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.

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

~~~
mmhsieh
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?

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

~~~
detaro
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.)

~~~
ehnto
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!

------
iscrewyou
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...](https://dot.ca.gov/programs/design/ccs-standard-plans-and-standard-
specifications)

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

------
NikolaeVarius
> Concrete creates greenhouse gas

I guess its time to also shame walkers and sidewalk bikers

~~~
cjsawyer
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.

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

------
nabla9
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?

------
gwbas1c
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?

~~~
winrid
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...](https://www.quora.com/Why-do-roads-turn-grey-when-they-get-paved-
black?share=1)

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

~~~
wongarsu
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.

~~~
UnpossibleJim
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.

~~~
wongarsu
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.

~~~
MayeulC
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).

~~~
saagarjha
> can use the rails as conductors

But then bad things happen if you touch them…

------
dboreham
Smells so good though.

------
airdropsBMW
It's a super cool paper

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ffpip
The roads near my house -
[https://economictimes.indiatimes.com/videodash.cms?autostart...](https://economictimes.indiatimes.com/videodash.cms?autostart=1&msid=70948040&rlvideo=1052732854&fallBackMute=true&skipad=false)

~~~
yboris
Do not click: 30 second unskippable ad.

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

~~~
ffpip
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?

~~~
totetsu
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.

