> Yeah, the question is if there's some sort of "traffic expands to fill the highways" argument

Yep, that's always a concern, and one of the reasons I framed my response around what the argument was, and what the claim was. I haven't really done enough research to know or feel confident in whether that claim is borne out or holds and the concern you've raised is the major thing that could get in the way.

I was largely just commenting on the disconnect in the discussion that I was observing.