If only we had other technologies for moving heavy things without using concrete roads

The USA already moves a higher percentage of freight by rail than almost any other country. But rail could never work for time-sensitive loads or last mile delivery.

You would be amazed at how much FedEx, UPS, and Amazon traffic moves by train. BNSF (at least) even has "guaranteed delivery" trains.

Last mile I will give you. Those shippers use trailers and containers on railroad cars, and trucks do the last mile delivery.

Perhaps they could make the rail lines and machinery smaller. One might even consider such rail to be "light", in comparison.

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.

Horses? I don't see how you really solve last mile.

Huh? I've had horses in my basement. The last mile was solved centuries ago.

Drones? For last mile delivery roads are the only game in town.

the freight has more axles, and you could set the baseline weight by vehicle class

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?!)

Segregating regulations by vehicle class is how the CAFE laws failed. Make your vehicle a “light truck” and now you can give it much worse mileage.

No, you just have to charge in proportion to damage done and let the economics work out how they will.

Good point, but one could probably easily treat freight vehicles differently.

No, they should be paying for their damage. Bring back local railroads if it's a problem. Add more axles, move less at once.