San Francisco faces a lot of problems which DC doesn't when designing a subway system. Apart from the fact that there's a honking great bay in the middle of the

San Francisco faces a lot of problems which DC doesn't when designing a subway system. Apart from the fact that there's a honking great bay in the middle of the metropolitan area, I'm not sure it's possible for BART to serve much more of San Francisco proper than it already does. Why? Well, if you go north of the BART line you're rapidly into the hills, so either you have to take the trains up the grade (bad idea) or you have to build your stations thirty storeys underground (also a bad idea). If you go past the hills and up to the Marina, you're into reclaimed land so I don't think it's possible to build a tunnel (civil engineers out there to comment?) You could probably extend it out into the Richmond and Sunset districts, but that part of town is served reasonably by buses anyway. While I hate to defend BART almost as much as I hate to ride on BART, its main purpose is really all about linking the cities of the East Bay with San Francisco, and San Francisco with the airport. Comparing it to a proper metro system in a city not subject to the weird geographical limitations imposed by the hills and the Bay isn't really fair.