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.