planning a trip, flying into IAD and was thinking about renting a car off airport site in Sterling, VA which saves me $75 just for three days. Would a taxi from IAD just go less than 2 miles from the airport, or is there a flat fee? I figure the driver would be pissed waiting in line for hours to get a cheap $6 fare. Other option is to take a hotel shuttle to the Doubletree and get a cab from there? Off site rental office closes at 6pm and the flight touches down at 4pm. This is all carry-on.