On Fri, 15 Jul 2011 02:01:40 +0100, Clive
wrote:

In message
,
W14_Fishbourne writes
However, I am a bit mystified why the door interlocking doesn't (a)
just prevent power being taken when a door is open rather than, as the
implication is here, (b) allowing power to be taken then cutting it
off if a door is open. Presumably interlocking of type (b) also covers
the event of a train door coming open while the train is moving,
giving two levels of protection for the price of one.
In my time on both the Northern and Central lines trains were frequently
moved around depots with the doors wide open, if only to get some fresh
air through them.

In pre-OPO times it was not uncommon for trains to leave the carriage
shed at Queens Park with the doors open during the Summer.