Eric over at Transbay Blog made some comments in the Livermore Thread that rang true for many people in San Francisco and other big cities with half finished metro lines. I too wish we had a real metro system in the Bay Area. It certainly would make getting more places much easier. And I have a feeling that it would increase ridership dramatically.
Why do I think we should invest more in urban subway systems? Because these lines have been driving national ridership gains over the last 15 years. (data here). Heavy Rail has produced about the same gain as bus, light rail, and commuter rail combined. Obviously there are different modes for different purposes. But some corridors need a metro, more than BART has now. Perhaps we should start a campaign? The Urban Subway Expansion Project. Any other cities that should join? I nominate LA first.
So where should we put new subways? In the Bay Area.... we'll just make a map. Any corridors? I'll start with Geary haha.