I think there's one point with regard to philosophy. The point is this: Can we afford it, and can we afford not to do it? In many cases, that “not” situation is something we have to consider. Can we allow these cities to grow without helping the people move around them? That's philosophy.
That's the first step with regard to understanding the problem. Then, as you were saying, we get into the situation of the municipalities. Invariably they have no money. So how do they get money? A gas tax may be one solution. It all depends on the kind of system we're talking about too, and how big the actual urban city is.