I'll move this to the Washington D.C. Forum where there are numerous threads/posts on this topic such as:
Originally Posted by
bhatnasx
From IAD to DCA (and vice versa): The most economical way, if you have at least a 4 hour connection, would be to take the combination of the metro & the 5A bus. If you have at least 3 hours, then the best way would be to take the Washington Flyer bus & then the metro rail (and others, feel free to correct me if I’m wrong). The fastest way would be SuperShuttle or a cab. I think a cab would be about 50-60 bucks.
FlyinHawaiian, Co-Moderator
United MileagePlus Forum