Do we need more highways?

This question should provoke an interesting debate on the National Journal‘s transportation blog.
The question is raised in the context of a survey done by the U.S. Conference of Mayors, showing, not surprisingly that mayors are fans of transit. As the discussion is framed by Fawn Johnson: “New highway construction is lucrative and sexy, and thus easier to win political support for it. Road maintenance, by contrast, is boring. Public-transit investments can also cause difficulties because they set up disputes between urban and rural areas.
“Are the mayors right that the United States doesn’t need any more new highways? If they are wrong, where should new highway construction take place? If they are right, how should infrastructure spending be allotted among public transit projects and road and bridge maintenance? Does it make sense to devote any gas tax funds to public transportation?”