> no, unless you count any passenger rail or air systems as "successful" and "private." But that's not really a sufficient argument.

Well actually that is not bad. I mean air systems are private and they work. So a good argument. Not without heavy regulation but nevertheless. Now, one can argue that looking at just aircraft flying in the sky is not enough, one has to obviously look at airports. And there it is back to government allocating and sponsoring development.

What about passenger rail? I can't think successful modern national-level private passenger rail systems.

> Does that mean I don't get to propose new solutions and argue for why I think they should work?

Sorry, I meant the difference between just showing that highways produce some inefficiencies. That is not hard to do, it is a simple argument in a way. Some imminent domain is taken, government paid for some of it. Makes rail more expensive, so can't quite compete with it. Is that a basic rehash? A more interesting argument is to propose something that works. Say, privatize roads. How would that work and why are there no large scale examples of it, if it is supposedly a good idea.

> I can make an argument for how libertarianism

I guess I misunderstood your argument as more being about showing an inefficiency in a government run project. That is not too hard. But what to do about it. It might seem "privatise" is the clear answer. But the other answer is "not have it at all" or have something else, or even enhance government control over it.

We are almost there with the post office. It is inefficient, outdated, and dying. But it still delivers mail to places where it makes no financial sense to deliver for someone like FedEx. If USPO shut down, I think necessarily in many places there would anything in its places. Maybe that is the correct answer or maybe it isn't.