Originally Posted by
Alpha Golf
No it's Metro only. You can't use the paper farecards on the bus at all.
Definitely recommend MARC is it's weekday.
On a weekend, I'd still consider Amtrak at $15 for a NE Regional train. If you don't have to wait too long for the shuttle from BWI to the BWI rail station (sadly, not a given), it's about 35 minutes from there to Union Station. That's only a few minutes longer than the B30 takes to deposit you at Greenbelt Metro, from where you have a long ride to downtown--longer on weekends if you're on the wrong side of Metro maintenance.