I feel like this means taxes should be imposed on cars proportionally to the fourth power of axle load too.
Last mile I will give you. Those shippers use trailers and containers on railroad cars, and trucks do the last mile delivery.
I'm sure it's pure coincidence that many cities already have rail lines going down roads in city centers. They probably just built the city around a historical freight line, and haven't bothered to remove it.
but maybe this would just incentivise the sort of person that buys an F150 to drive to the shops to simply to upgrade to a big rig (for the tax saving?!)
No, you just have to charge in proportion to damage done and let the economics work out how they will.
Massive increase in the cost of public transport as buses pass their tax costs onto users.
Massive increase in the cost of freight shipping, which would be passed on to consumers, i.e. everybody, since virtually every part of the economy depends indirectly on freight transport.
It would amount to everybody paying, and thus being more or less equivalent to public funding of roads.
You could obviously tweak legislation to treat such vehicles differently if you wanted. I was just getting the core idea across, not suggesting my comment should be copy-pasted verbatim into the next bill Congress is passing.
Public Transport -- If tax payers are currently paying for the external costs of public transportation (via taxes to repair roads) then it won't cost anymore public money if taxpayers continue to cover that cost. For private busses this is a case of tax payers unfairly subsiding their external costs.