Older style narrow gauge driverless underground electric train in the GPO 
workshops at Mount Pleasant, London on 7 June 1996. There are two voltages 
(110 volts for slow speed in station areas and 440 volts for main line 
operation at up to 30mph).  When the train enters an unpowered section the 
electromagnets are de-energized and the brakes applied so that the train 
stops at a pre-determined loading spot.

Copyright Pat & David Othen, Dartmouth, Nova Scotia, Canada 
(dothen@ra.isisnet.com)