[mothballed]

No tax I've seen is anywhere remotely close to following "fourth power law" on axle weight[]. And especially so for gas taxes, as the gas/diesel cost tends to be closer to linear with weight.

Usually what happens is smaller cars subsidize everyone else due to paying a disproportionate tax vs axle weight^~(2-4 depending on fatigue pathway). Depending on tax structure possibly pedestrians/cyclists too but they are usually parasitic on tax basis.

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

[mavhc]

Agreed, tax based on damage to road, and then tax fuel the amount it costs to clean up the pollution the fuel causes, and then use the money to clean up the pollution it causes. Then who cares if you fly your private jet, or giant car, you just pay for it.

Side effects include: reduced pollution, and cheaper ways to clean up pollution

[mjlee]

I don't disagree that large cars create externalities, but what proportion of costs scale with axle weight?

In the UK the most recent budget allocates £1.6 billion for maintenance. According to statista £13 billion was spent on roads last year.

https://www.statista.com/statistics/298675/united-kingdom-uk...

[michaelt]

Basically, it’s well known that fully laden 44 tonne articulated lorries making sharp turns do a lot of damage to roads.

That’s who in industrial estates you’ll often find concrete roads, instead of tarmac, for lorries making 90 degree turns.

American style trucks might be big, but presumably they’re nowhere near 44 tonnes.

Of course, articulated lorries only drive on major roads; your average residential road gets no lorries, so all the wear is from smaller vehicles.

[jeltz]

44 tonnes is not that big. Sweden allows for the insane limit of 64 or 74 tonnes, depending on the road. American trucks are typically smaller than European.

[rascul]

> American style trucks might be big, but presumably they’re nowhere near 44 tonnes.

I believe the typical limit is 40 tons. I don't know if our tons are the same as your tonnes.

[Aloisius]

The US limit is typically 80,000 lbs, so 36.29 megagrams (aka "metric" tons).

The EU countries have limits of 40 Mg or higher (except Albania). Netherlands allows vehicles up to 50 Mg.

Of course this is all for 5+ axle vehicles. A 5-axle 40 Mg big rig is putting a 8 Mg of load on each axle (if it was perfectly distributed).

A Dodge RAM 1500 loaded up has a gross vehicle weight of about 3.27 Mg - about 1.64 Mg/axle. Fourth power law means about 566 loaded RAMs would equal one about 40 Mg 5-axle big rig in terms of road damage.

[yurishimo]

They’re close enough as to not matter a whole lot for this discussion.