There are also 4 or 5 Mr. Easy check ins upstairs very close to security as the previous poster said, and some along the checkin areas as well for people queued up to check baggage. Security lines move quickly at IAD. Keep your ID and BP handy for the first checker in the security line, and then just the BP as you go through the detector. Mobile lounges leave every 5 minutes, ride is about 5-8 minutes. Time to gate can vary if you are at C-1 or D 15; it can be 7 or 8 minute walk. Corridors in the terminals can be surprisingly crowded at times. You may want to consider buying a 1 day RCC pass for $50 if you are doing an all day MR and have time between flights. Some folks have posted free ones on CC forum that expire the 31st. Happy Travels.