[ardecila]

The problem (understandably) is a reluctance to do transfers between modes. MARC and VRE have scraped along for years with minimal facilities, so the transfer facilities are terrible. DCites are not used to pleasant or efficient transfers out of the Metro system. I'm thinking of New Carrollton, Greenbelt, Silver Spring, etc - the places where commuter rail and Metro have adjacent stations. Transfers are confusing, hard to reach, and the stations are barren, unpleasant places to wait. Long train headways, as you point out, don't improve the situation.

I agree that VRE is a much better transportation TYPE than Metro, in exactly the corridors that are being discussed (I-66/West, I-95/Southwest). If the DC area continues its most-favored status when it comes to transportation funding, it should invest in DMU or EMU service on the VRE tracks. The Orange Line to Centreville seems like it could be answered better with a BRT network feeding into Fairfax-Vienna Station, and the Blue and Yellow Line extensions seem highly redundant, as they would approach each other near Fort Belvoir.

Of these, the most sensible one is Blue Line to Fort Belvoir. It has an existing corridor and it promises to serve a major employment center. But can Metro really serve a dispersed military facility effectively? Perhaps a feeder BRT network, with a dedicated road or dedicated lanes to Franconia-Springfield Station, would be more appropriate.