Pyrrhus said:
The real purpose is a direct charge to pay for the costs.
On the surface perhaps, but to many in government, the real purpose probably is control.
Automobiles represent everything about society that utopians and social planners hate, because it represents freedom. You think the Left would even let people drive cars if they could prevent it? I don't think so. I think cars would be regarded like they firearms, too dangerous for the general populace to drive by themselves, something that should only be left to experts or people with special licenses. They cannot do this however because without automobiles, society would cease to function.
The Left have a natural inclination to utopianism (so do the far Right, but it's a free-market utopia they adhere to). If you look at all utopian visions of the future, if you notice, almost always automobiles drive themselves. Remember the freeway in "I, Robot," where the vehicles all are self-driven, and when you park your car, a big machine comes out and snatches it up into storage? In the book
3001: The Final Odyssey by Arthur C. Clarke, when the main character wakes up and finds he is now about one thousand years into the future, he also is told that now it is mandated by the government that everyone shave their heads to wear a special monitoring device on their their head. These are just some fantastical utopian visions perhaps, but the Left are prone to them and very prone to making attempts at trying to create such societies. However, automobiles that people can hop into and freely drive anywhere and any time they want, shatter attempts at this entirely.
Because the automobile is not something the government can control (yet). The idea of millions of people all just driving themselves anywhere they want, anytime they want, with zero government oversight, just is maddening to some of those with utopian schemes I'd imagine. I also believe this is the reason for the Leftist obsession with high-speed rail. They tend to despise America's cheap gasoline, big SUV's and pickup trucks, and the Interstate Highway System. They much prefer the European model of high fuel taxes, and hence expensive gas, thus forcing people to drive smaller vehicles, and take high-speed trains throughout Europe as opposed to a system of big highways. Trains run on a fixed schedule and follow fixed routes and are thus another way for the government to control people.
Your economics I find very interesting, but with the reasoning you're giving, if/when computers are invented that can drive vehicles by themselves, with no human interference whatsoever, you'd then argue that a policy should be made that it be made mandatory that all cars be self-driven so as to cut down (or even eliminate) car accidents and so forth. A per-mile tax is one of the best ways for the government to control the behavior of the masses driving their automobiles. It allows the government to track when, where, and which way people drive full-time. It may make for more efficient traffic, but that doesn't mean it is the right way to go about it when we have a society focused on freedom.
No more so than if having every car automated would eliminate traffic accidents means the government should mandate all automobiles be automated. I also disagree with your assertion that "it's going to happen." Maybe in Europe perhaps, but in America, I think you will end up with too much of a public outcry. The Courts have decided we have a right ot privacy guaranteed by the Constitution, so I would imagine many would claim such a policy would violate it.
