Da quel poco che ho potuto vedere il Dulles e' collegato solo tramite Bus, oppure bus e metro
Per altri collegamenti su Philadefia and NY dovresti prendere il bus fino alla Union Station e poi da li' prendere Amtrak.
Se vai sul
sito dell'aeroporto Dulles troverai queste info:
How to connect to the Metrorail system from Dulles Airport:
Purchase a ticket (one-way or round-trip) at the Washington Flyer Coach ticket counter located at Arrivals Door #4 in the Main Terminal. Travelers will also board the Coach from this location. The buses depart approximately every 30 minutes but please listen for announcements for exact bus departure timesYou may purchase a Metrorail fare card inside the train station at the West Falls Church Metro stop where you will board the train. Trains bound for "New Carrollton" will take you towards Downtown Washington, DC.