 The engine that pumped each section was the one towards which the train was travelling, for example a train leaving Exeter was powered by the Countess Wear engine creating a partial vacuum in the pipe in front of the train which was then propelled forward by the normal atmospheric pressure in the pipe behind the train's piston.Pumping started up to eight minutes before the scheduled departure of the train so as to build up a sufficient vacuum.At stations a smaller pipe was laid alongside the track and a piston in this was connected to the train by a rope to start it moving.