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Comment by 8by3 | Hacker News Reader

Seems electric cars produce the same or sometimes more non combustion particulates than ICE cars, eg. bits of road and tire that are flung into the air while driving.

So EVs are better than ICE for air quality, but fewer cars even better.

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I think that particle size is important.

Particles caused by tyre and brake wear are going to be much larger than, say, diesel particulates.

That size differences is going to affect how easily they can be absorbed into your lungs.

I think it’s mostly break dust. Electric cars are heavier but can also hopefully mostly use regenerative breaking instead of break pads. Road vibrations (and wear?) tend to go as the fourth power of weight over the axle and so it tends to be worse for (naturally heavier) electric cars but even worse for goods vehicles.

But london tube have order of magnitude of dust pollution and buses damage roads (aka pollute) 30,000 (yes 30k) times more due to weight.

How do you get 30k?

A new Routemaster double decker weighs 12.6 tonne and carries up to 80 passengers. A typical car weighs 1.6 tonne and carries up to 4 passengers, they both have two axles. If we guess at half the rated passenger count then we have:

  Bus damages the road (12.6/1.6)^4 = 3845 times as much as a single car.

But it carries 20 times as many people so the damage is only 192 times per person. Still a lot of course but other pollutants such as NOx are surely so much less that it can be justified.

I'm sure my calculation is imprecise but surely not that far out. What have I missed or misunderstood?

You forgot the passengers. Gross weight of electric double decker is 19.2 tones. (19.2/1.6)^4=20,736.

Which also means roads for heavy transport is 20k times more expensive!

Surely the relevant metric is danger per passenger so your 20 k needs to be divided by the number of passengers, that takes your 20k down to 20k/80 = 250.

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