All of those other systems have multi-system terminals. Penn Station, Grand Central etc. You can literally walk across the hall in the same building and change trains. In Bethesda you will need to exit the station and walk around the corner to the other station entrance to transfer between Metro and Purple Line.
steelgame1975 t1_j1z91ko wrote
Reply to comment by ad-lapidem in Questions about the Purple line? by liquibasethrowaway
All of those other systems have multi-system terminals. Penn Station, Grand Central etc. You can literally walk across the hall in the same building and change trains. In Bethesda you will need to exit the station and walk around the corner to the other station entrance to transfer between Metro and Purple Line.