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Comment by ndsipa_pomu | Hacker News Reader

Weight is an important metric as it has a big influence on two very important external affects.

Road wear/damage is proportional to roughly the fourth power of weight. However, this won't have much impact on SUVs directly, but on large lorries and buses. (It's easy to see the damage at bus stops where the slowing to a stop and starting from a stop, both noticeable deform the road after a time. This is also visible at traffic lights.

Tyre and brake pollution are very closely tied to the vehicle's weight, which leads to the issue of EVs producing almost as much total pollution as a lighter ICE vehicle even though they don't produce exhaust pollution. Tyre pollution is one of the most insidious types of pollution due to the size of the particulates and the chemicals used in tyres.

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> However, this won't have much impact on SUVs directly

Why not?

Even an increase from 1.5 tons to 2 tons results in 3.16x the damage on the road.

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

If that weight difference results in a noticeable tax difference, then lorries will be virtually priced off the road due to the tax. Realistically, the tax would have to be affordable for heaviest vehicles which would make the tax difference between 1.5 to 2 tons negligible.

Maybe one way round it is to have tax bands for heavy commercial vehicles and weight-based tax for cars and SUVs.

Edit: thought I'd try to work out an example of pricing.

If a fourth power tax rate on weight works out to a £100 difference between 2 tons and 1.5 tons, then an 8 ton vehicle would be paying over £37,000

> If that weight difference results in a noticeable tax difference, then lorries will be virtually priced off the road due to the tax.

That’s a red herring. Lorries don’t have to be taxed the same way as cars, and actually most of the time are not.

They absolutely are taxed much heavier than most cars. Truck are charged on most highways in European Union, I expect UK has similar system. They pay per-km driven.

I am addressing the “but higher taxes will put companies out of business because lorries” straw man that appears a couple of times in the discussion. Taxes for family cars and for professional vehicles are effectively decoupled and can be adjusted independently.

If all cars are responsible for some small fraction of road damage, it probably isn't going to have much impact to carefully apportion that fraction of the damage.

> That’s a red herring. Lorries don’t have to be taxed the same way as cars, and actually most of the time are not.

Yes, but I can see it being unpopular to introduce a "road repair" tax that is justified based on drivers paying for the damage that they cause to roads and then not apply the same rules to the vehicles that cause the majority of the damage.

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