Privatizing all roads would ironically probably be the fastest way to cut down on oversized vehicles. Nobody wants to pay a quadratic weighted toll on the GVWR of a bunch of extra SUV, but when they have to pay it all in taxes non-quadratically anyway it's a fuck it go big moment.
Let's see... If we privatize roads and every owner (pinky promise) only makes everyone pay basod on vehicle weight... That almost sounds like a tax based on car weight.
https://en.wikipedia.org/wiki/Fourth_power_law
Also, squishy humans really prefer to not be hit by heavier objects travelling at similar speeds.