This is the right idea, but let's not stop there. Why not also tax privately registered vehicles to some degree by their mass?

I also like the idea of making fines for moving violations somewhat proportional to vehicle mass. The danger posed to others by a 150 lb moped pales in comparison to that of a 4500 lb pickup truck. At least in the U.S., a ticket for speeding 50% over the limit through a residential neighborhood is the same for both, for example. Neither is OK, but considering the disparity in the potential for damage and injury to others, imposing equal fines is insane.

Because "privately registered" vehicles don't matter for purposes of road damage.

A fully loaded semi is 18,000 lbs per axle. A really huge personal vehicle, an F-350, is 4000 lbs per axle. That's 4.5x the weight, 4.5^4=410, so the semi is doing 410x as much damage. There's really no point in trying to tax personal vehicles for road damage when over 99% of the damage is being done by trucks.

The GVWR on a F350 is around 10-14,000, so somewhere between 5-7k axle load.

Yes that's the gross weight, i.e. carrying its maximum rated load. Personal vehicles are very rarely loaded up to their maximum weight, and mostly are driven relatively empty.

Even driven at gross weight, it's doing 5% of the damage per axle of loaded semi. The semi also has 4-5 axles, so it's more like 2% of the damage of the semi.

Mind you, we're talking here about the most damaging personal vehicle loaded to its maximum weight, and the semi is still doing 50x the damage of the personal vehicle. It's reasonable to say that essentially all road damage is done by semis.

For the most part I agree. The other issue is psi load produced by different tread patterns. Going from some minimal water channels to a mud terrain cleated style will reduce surface area a good bit. If you have experience with rural areas you don't need a calculator to observe the highest direct damage is usually from agricultural tractors. Deformation from a single pass can be observed (and often felt) with the naked eye in many cases.

Well, after all, the whole point of these tires is to dig into the "road" to get better traction than is possible with normal friction, so it's not too surprising that they dig in to a lesser extent on hard surfaced roads.

That said, this type of tire is a very tiny fraction of the total miles driven on public highways, and so if you're looking for someone to tax based on the costs they create, it's all heavy trucks.

Where are you getting your "over 99%" figure?

You need to approach or exceed a roads per-axel weight limit to do any damage or serious wear.

Trucks and permit loads are pretty much the only things that get close.

Beyond the elastic limit, damage is an exponential function of the pavement loading, but only once that certain minimum psf is hit.

For the majority of a highway's loading curve, the damage-per-force is essentially nil. Plastic deformation and serious fatigue only start as you approach the design limits.

It's 99%+ because cars don't do any real wear or damage to pavement from typical use.

A semi is doing 400x as much damage as essentially the heaviest personal vehicle driving. For a more typical car at 4000 lbs (2000 lbs per axle), the semi does 6000x as much damage. If semis are 2% of all traffic (true in my observation), they're doing over 99% of the damage to roads. It makes no sense to care about road damage at all from any vehicle other than a heavy truck.

In my state, we're implementing a cost per mile for vehicle registration purposes. I think the idea is tied to air quality concerns, but a similar model would work for road maintenance.

I just wonder what would happen if we charged trucks based on weight.

Thats certainly one solution, and a perfectly reasonable one at that. It seems to be an excellent way by which we can also encourage more rail development, and reduce the overall amount of waste in the transport chain.

You'll also see trucks use more axles with wider, softer tires. It's easy to get more than an order of magnitude in damage reduction.

Which is always easier said than done and a bit simplistic. The primary factor derived to date has been to tie the wear factor to axle weight. Meaning an empty vehicle made for transporting goods would be in the range of passenger vehicles. In addition to simple overloading, improperly balanced loading represents more damage for the same total vehicle weight. So each axle must be weighed in a loaded state on each individual trip to determine the presumptive proportional tax burden.

All of which creates overhead in the form of people to be paid, equipment to build/own/maintain, time lost at all stages, the usual political influence problems, jusrisdiction of different areas of road, implementing policy, and corruption. Most of it will end end up as pass through cost to individuals either way as both consumer goods and roadways are deemed essential. It's ultimately a fairness exercise of tax distribution so like most things in the public interest the arena any idea must be fought in is politics.

Don't we already weigh trucks as they enter and leave the state, as well as sometimes in the middle of the state? I don't know what goes on there already, but we could certainly charge trucks based on loaded miles in the state, which should be pretty easy to calculate since they have very predictable driving patterns and take fairly detailed logs. For local deliveries, we could just charge based on the max load and allow drivers to prove anything otherwise.

And yes, consumers will pay regardless, but at least the difference is reflected in the cost of goods. It could very well be that certain local goods are cheaper than imported goods after road costs are properly factored in, which could change how much is imported.

However, this feels a bit regressive since poorer people will pay more of the cost since roads are largely funded by income tax, but that can be accounted for by shifting other taxes. The idea isn't too punish poor people or shipping customers, but to allow the market to work more efficiently.

Shouldn't roads that are heavily trafficked by trucks by made out of concrete instead of asphalt? Surely it's known that it lasts much longer, I guess the question is if it's economically viable considering long term costs.