In message , Clive Coleman
writes

And they'll be even more annoyed if they ever find out that LU shut T4
station a day early just so they can get their trains all pointing the
"right way around", when every Picc depot seems to have coped fine
with trains in random directions every night since 1987.

This is just luck that no train has broken down in a tube section and
need assistance from the rear.

That bit's easy to do. I've known pushouts to happen two or three times
in the past three years. Mechanical coupling isn't the problem, it's
getting the two bits of train to talk to each other electrically that
needs them to be correctly aligned.

An 'A' end unit won't/can't talk to another 'A' end unit, just a 'D' end
one, and the 'D' end units can't talk to another 'D' end unit, just an
'A' end one. The three car units (half a train) are frequently split
and re-coupled in depots and this would be a nightmare if all the trains
were different ways round. As I pointed out earlier, this is currently
got round by sending a train round the loop to turn it if required.
After 8th Jan, this won't be possible so they are making sure they all
face the same way before the event, so we'll be just like all the other
lines (well, most of them anyway).
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)