I was interested by the passenger trasport system used at Washington Dulles.
See below,
The ‘bus’ can either take passengers on board by means of direct entry from a terminal building or people can enter from ground level. Apparently this might be the only airport in the world that uses this system. I am told that the system is soon to be replaced by a new system involving an underground train system.
Some history of the ‘mobile lounges’ here, Jim – http://www.metwashairports.com/dulles/about_dulles_international_2/history_2
They have been there since 1962!