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Here is the Yale press release: https://news.yale.edu/2020/09/02/asphalt-adds-air-pollution-especially-hot-sunny-days https://news.yale.edu/2020/09/02/asphalt-a
by nickff 6y ago
Here is the Yale press release:
https://news.yale.edu/2020/09/02/asphalt-adds-air-pollution-especially-hot-sunny-days https://news.yale.edu/2020/09/02/asphalt-adds-air-pollution-...
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 6y ago> 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 6y agoNo, 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.
- Valgrim 6y agoFor 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.
- shajznnckfke 6y agoFor 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.
- melling 6y agoSounds like we need to expand our rail capacity. Our current rail freight capacity is near 100%.
- gruez 6y agoWhy not tax each mode of transportation proportionately to their true cost, and let the market decide?
- melling 6y agoHow 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?
- Taek 6y agoYes, 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.
- epistasis 6y agoWe 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.
- lostapathy 6y agoLarge pickups aren’t an appreciable part of the problem here - 18 wheelers are.
- mirkules 6y agoThe 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.
- CameronNemo 6y ago>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_States https://en.wikipedia.org/wiki/Fuel_taxes_in_the_United_State...
- mirkules 6y agoActually, 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.
- throwaway0a5e 6y agoPairing those questions with skepticism of government certainly didn't help.
- 6y ago
- cameldrv 6y agoYou 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.
- adwww 6y agoExcept in Europe, where Diesel peaked at almost 50% of all vehicles sold - pre dieselgate.
- lostapathy 6y agoThat 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.
- deleted 6y ago[deleted]
- nickff 6y agoA 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.
- zip1234 6y agoTires wearing out is indeed a source of pollution though. That material wears off onto the roads.
- wolfram74 6y agoI 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-weight-vs-road-damage-levels/ https://streets.mn/2016/07/07/chart-of-the-day-vehicle-weigh...
- marcosdumay 6y agoIt'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.
- LeifCarrotson 6y agoVehicle 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.
- yread 6y agoWhat effect does tire width have? Very narrow (<165mm) tires vs dual tires of trucks for example. Smaller area of friction versus lower pressure
- serf 6y ago>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.
- 6y ago
- throwaway0a5e 6y ago>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.
- namdnay 6y agoHence the caveat “approximately proportional”
- enkid 6y agoEven if it's a ballpark figure, the GP's statement would still be correct, no?
- nafey 6y agoAs 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.
- deleted 6y ago[deleted]
- crazygringo 6y agoThe 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.
- Retric 6y agoThe 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.
- apendleton 6y agoIt 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?
- jemfinch 6y agoRoad wear is what makes communities repave roads, so cars vs. trucks has quite a bit to do with it.
- abdullahkhalids 6y agoYes, 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?
- lrem 6y agoUh, 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.
- NeutronStar 6y agoThere's what, 10M truck driver in the US? It's pretty safe to say trucks are at least 10x worst than cars on the road.
- tlbsofware 6y agoCould this problem be temporarily mediated by expanding the width of tires to increase the surface area and disperse the weight?