3 ms·

Climate yes, but air quality not by as much as you'd think. Multiple studies have come out showing that the weight of EVs puts more pressure on tires and breaks

by tedivm 3y ago

Climate yes, but air quality not by as much as you'd think. Multiple studies have come out showing that the weight of EVs puts more pressure on tires and breaks, which in turn increases the particles they dump in the air. > As a result, total PM10 emissions from EVs were found to be equal to those of modern ICEVs. PM2.5 emissions were only 1–3% lower for EVs compared to modern ICEVs. Therefore, it could be concluded that the increased popularity of electric vehicles will likely not have a great effect on PM levels. Non-exhaust emissions already account for over 90% of PM10 and 85% of PM2.5 emissions from traffic. These proportions will continue to increase as exhaust standards improve and average vehicle weight increases. Future policy should consequently focus on setting standards for non-exhaust emissions and encouraging weight reduction of all vehicles to significantly reduce PM emissions from traffic. As the quote mentioned, this can be improved. Lighter batteries, better regenerative breaking, and improvements in tire material would all help. https://www.sciencedirect.com/science/article/abs/pii/S135223101630187X https://www.sciencedirect.com/science/article/abs/pii/S13522...

dkjaudyeqooe 3y ago
I wonder if it would make sense to program robotaxis to use only regenerative braking, maybe with a more powerful regenerative braking system, and using real brakes only for emergencies.
- magnuspaaske 3y ago
  That's how most electric cars are set up already
shiftpgdn 3y ago
I feel like this is a nonsense study. They used a 2013 study that measured gas cars and then just extrapolated that out based on weight for EVs and did nothing to account for regenerative breaking, specialty EV tires, etc. Also the numbers are from the Simons 2013 study seem to be dubious as well. Anyone who has been to Oslo understands EVs are a huge benefit for urban air quality.
- xnx 3y ago
  On top of that, the Waymo vehicles are much more efficient drivers: no rapid acceleration, no hard braking, lower top speed, etc.
magnuspaaske 3y ago
This is the wrong way to think about it since there's little that suggests AV-taxis also need to be larger than the cars already on the road. When I'm renting a car or taking a taxi I know exactly what my needs are and can decide to not pay for luggage space if I don't need that for instance. Further you can just put a smaller battery in AV-taxis since you can optimise the charging schedule. And lastly, when we've gotten rid of air pollution from tailpipe emissions air pollution from tires would be the next problem to fix and it intuitively seems that all electric, digital cars could have their pollution reduced via a software update. And obviously the technology making these cars possible also make self driving busses possible, which would allow new ways for urban mobility.
zizee 3y ago
This is interesting/surprising and I would like to learn more, but the linked study is truncated behind a Paywall.
cyberax 3y ago
> Climate yes, but air quality not by as much as you'd think. Multiple studies have come out showing that the weight of EVs puts more pressure on tires and breaks, which in turn increases the particles they dump in the air. This is total bullshit. EVs barely use frictional brakes at all. My Tesla Model S from 2014 is still on the original set of brakepads after nearly 200000 miles. Several EV car models even have a problem with disks _rusting_ because the frictional brakes are not used except when the car is parked. If anything, EVs will absolutely cut down on brake dust. With tires, it's a bit more nuanced. Regular tires can indeed wear a bit faster on an EV, especially if you are addicted to high acceleration. But tire vendors are now producing EV-optimized tires that are a bit more durable, and it seems like the difference is pretty negligible. Also, keep in mind that your bullshit study only looked at weight. So it follows that buses and trucks (that have MUCH more weight) will leave genocide and devastation in their wake.
r00fus 3y ago
One thing that caught my eye is the study is simply modeling the increased PM10 and PM2.5 based on hypothesised influence of weight difference using gas and diesel cars (from 2013) as a basis. Obv. I haven't read anything but the summary but the core assumption means it's an extrapolation and not measuring actuals. For example, while EVs accelerate faster, regen braking massively reduces brake wear - the lack of mention of regen in this extrapolative study seems a huge miss. Also EVs typically don't have the same tire material - they use low rolling resistance tires which do better on particulates.
chroma 3y ago
I'm suspicious of that paper. The largest source of non-exhaust emissions comes from brake pad wear[1] and EVs use brakes far less than combustion vehicles. Also the amount of particulate matter put into the air is highly dependent on vehicle speed. Densely populated areas have more traffic, which means cars drive slower and create less non-exhaust pollution. And it's no longer true that EVs are heavier than comparable combustion vehicles. The Tesla Model 3 weighs 3,550-4,070lbs. The BMW 3 Series weighs 3,200–4,330lbs, though the lightest model is a two door convertible. While combustion vehicles don't carry heavy batteries, they do need exhaust systems, more complicated drivetrains, and bigger cooling systems. Also, more and more combustion vehicles are becoming hybrids to meet stricter emissions standards. That means adding weight for batteries, an electric motor, and a transmission that can handle both propulsion sources. 1. See figure 6 in this paper: https://www.mdpi.com/2073-4433/12/2/190 https://www.mdpi.com/2073-4433/12/2/190
- jeffbee 3y ago
  As I understand it a large component of the particulate emissions from cars is resuspended road dust, so it doesn't really matter than an EV or hybrid has little of its own brake dust. The brake dust is already on the ground.
  - brewdad 3y ago
    But like CO2 emissions, the amount of brake dust available to be kicked up will decrease as more EVs take the road.
    - xnx 3y ago
      This isn't even accounting for the efficiencies of an autonomous vehicle decelerating less by better anticipating/timing stoplights. I see so many human drivers keep accelerating into a yellow/red light instead of easing off the pedal so they can resume accelerating by the time it turns green.
Waterluvian 3y ago
This sounds completely ridiculous.

by tedivm 3y ago

dkjaudyeqooe 3y ago

I wonder if it would make sense to program robotaxis to use only regenerative braking, maybe with a more powerful regenerative braking system, and using real brakes only for emergencies.

magnuspaaske 3y ago
That's how most electric cars are set up already

shiftpgdn 3y ago

I feel like this is a nonsense study. They used a 2013 study that measured gas cars and then just extrapolated that out based on weight for EVs and did nothing to account for regenerative breaking, specialty EV tires, etc. Also the numbers are from the Simons 2013 study seem to be dubious as well. Anyone who has been to Oslo understands EVs are a huge benefit for urban air quality.

xnx 3y ago
On top of that, the Waymo vehicles are much more efficient drivers: no rapid acceleration, no hard braking, lower top speed, etc.

magnuspaaske 3y ago

This is the wrong way to think about it since there's little that suggests AV-taxis also need to be larger than the cars already on the road. When I'm renting a car or taking a taxi I know exactly what my needs are and can decide to not pay for luggage space if I don't need that for instance. Further you can just put a smaller battery in AV-taxis since you can optimise the charging schedule. And lastly, when we've gotten rid of air pollution from tailpipe emissions air pollution from tires would be the next problem to fix and it intuitively seems that all electric, digital cars could have their pollution reduced via a software update. And obviously the technology making these cars possible also make self driving busses possible, which would allow new ways for urban mobility.

zizee 3y ago

This is interesting/surprising and I would like to learn more, but the linked study is truncated behind a Paywall.

cyberax 3y ago

> Climate yes, but air quality not by as much as you'd think. Multiple studies have come out showing that the weight of EVs puts more pressure on tires and breaks, which in turn increases the particles they dump in the air. This is total bullshit. EVs barely use frictional brakes at all. My Tesla Model S from 2014 is still on the original set of brakepads after nearly 200000 miles. Several EV car models even have a problem with disks _rusting_ because the frictional brakes are not used except when the car is parked. If anything, EVs will absolutely cut down on brake dust. With tires, it's a bit more nuanced. Regular tires can indeed wear a bit faster on an EV, especially if you are addicted to high acceleration. But tire vendors are now producing EV-optimized tires that are a bit more durable, and it seems like the difference is pretty negligible. Also, keep in mind that your bullshit study only looked at weight. So it follows that buses and trucks (that have MUCH more weight) will leave genocide and devastation in their wake.

r00fus 3y ago

One thing that caught my eye is the study is simply modeling the increased PM10 and PM2.5 based on hypothesised influence of weight difference using gas and diesel cars (from 2013) as a basis. Obv. I haven't read anything but the summary but the core assumption means it's an extrapolation and not measuring actuals. For example, while EVs accelerate faster, regen braking massively reduces brake wear - the lack of mention of regen in this extrapolative study seems a huge miss. Also EVs typically don't have the same tire material - they use low rolling resistance tires which do better on particulates.

chroma 3y ago

I'm suspicious of that paper. The largest source of non-exhaust emissions comes from brake pad wear[1] and EVs use brakes far less than combustion vehicles. Also the amount of particulate matter put into the air is highly dependent on vehicle speed. Densely populated areas have more traffic, which means cars drive slower and create less non-exhaust pollution. And it's no longer true that EVs are heavier than comparable combustion vehicles. The Tesla Model 3 weighs 3,550-4,070lbs. The BMW 3 Series weighs 3,200–4,330lbs, though the lightest model is a two door convertible. While combustion vehicles don't carry heavy batteries, they do need exhaust systems, more complicated drivetrains, and bigger cooling systems. Also, more and more combustion vehicles are becoming hybrids to meet stricter emissions standards. That means adding weight for batteries, an electric motor, and a transmission that can handle both propulsion sources. 1. See figure 6 in this paper: https://www.mdpi.com/2073-4433/12/2/190 https://www.mdpi.com/2073-4433/12/2/190

jeffbee 3y ago
As I understand it a large component of the particulate emissions from cars is resuspended road dust, so it doesn't really matter than an EV or hybrid has little of its own brake dust. The brake dust is already on the ground.
- brewdad 3y ago
  But like CO2 emissions, the amount of brake dust available to be kicked up will decrease as more EVs take the road.
  - xnx 3y ago
    This isn't even accounting for the efficiencies of an autonomous vehicle decelerating less by better anticipating/timing stoplights. I see so many human drivers keep accelerating into a yellow/red light instead of easing off the pedal so they can resume accelerating by the time it turns green.

Waterluvian 3y ago

This sounds completely ridiculous.