there are many many alternatives to using the interstates.
full privatization implies the buyer needs to have a 40-50 year perspective. Therefore, he can not overprice interstate use. If he does, then people will gradually move away. He’ll be stuck with a very expensive albatross with massive ongoing maintence costs.
Plus it’s important to realize a private owner will improve quality AND reduce costs versus government.
This is laughably untrue in my area and in a large part of the country with which I am familiar.
Taking a plane might be an alternative if you are traveling a long distance and live near an airport, don't need to bring much with you, and can arrange transportation on the other end.
Shipping goods by rail might be an alternative if you really have a lot of heavy items and live near a rail siding.
Driving on small state highways or back roads might be an alternative if you have lots of time to go a much longer distance and can get around natural obstacles.
This is not many, many alternatives.
Things might be headed in the direction you propose but I don't think it is right to call this a "free market" especially as it will be a guaranteed monopoly. It will be sort of like the situation where there is only one phone company or internet provider.
And just how many private company executives work on a 40 to 50-year perspective? Get real!
Also, in our current world, where by definition it is crowded where new capacity is needed, such private toll roads in essence work as private monopolies—taking away whatever theoretical basis for lower costs there might have been.
“...full privatization implies the buyer needs to have a 40-50 year perspective. “
Why? Everything other than the toll booths are already there. Why not 5 years and then open it up to re-bid?
I know the answer, of course, but I’m curious to see if you do.
Private has to price it attractively unless it is for all intents and purposes a monopoly created by the state because there are no other alternatives for travel. That is a sure enough public (political) private “partnership”. Have you been to Austin or Houston or tired to drive from Joplin to Tulsa or Oklahoma City without using a toll road?
Privitazition of public assets is not a solution for bad government management and it usually only leads to more corruption. Privitazition has only one motive and that is to make a profit above what the service costs. Not a modest profit but as much as the traffic will bear.
Pure capitalism is just as bad as pure socialism and eventually they are equal.