Also it should be noted that transit is much cheaper and much more efficient than highways. So if you are going to pay tax money to subsidize something transit is a much better choice simply because you get more bang for the buck.
Anyway you cut it it is cheaper to transport a single human than to transport a human traveling with a 2 ton metal shell around him.
To this I'd add the argument that transit is a public good - i.e. it benefits everyone, not just those who directly use it, by reducing congestion, reducing air pollution and GHG emissions, and encouraging the efficient, productive use of land and materials.
Highways, on the other hand, are a public bad (I think that's the technical term...) - i.e. they produce net negative externalities that must be borne by society as a whole.
Anyway you cut it it is cheaper to transport a single human than to transport a human traveling with a 2 ton metal shell around him.