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[email protected] · December 30th 03, 06:38 PM posted to uk.transport.london

In article ,
(Sharon & Gordon Thomson) wrote:

Have situations ever arisen on London Underground where major service
disruption has resulted from a track problem or derailment occurring at
a
critical location at/near a depot such as to prevent lots of trains from
entering service?
--
gordon

Can happen for various reasons and has happened on the Northern Line at
various times in the past. Depending on what and the problem is as to how
it affects the service. If an outlet road is blocked, then this could mean
the loss of all trains from that depot. At Morden, for example, the depot
is effectively divided into two - the north and the south sides. Each side
has its own outlet/inlet road and outlet signal. There are also two
crossovers that allow access from one outlet/inlet road to the other -
one after leaving the depot (the "shunters" crossover) and the other
leaving the platform when going to depot (the "regulators" crossover).
Because there is a steep gradient into depot, both roads have catch points
that will effectively derail a train if it rolls back entering depot.

Using Morden as an example, if there was a derailment going in or out of
depot, it might only affect one side. And trains could run in or out of
service from the other. If the other side was obstructed, or if the
derailment occurred going over the crossover from one side to another,
then both sides would be affected. In this case, no trains could enter or
leave depot.

The effect on the service would vary. If it was at start of traffic, then
a restricted amount or no trains may leave depot. It it was after the
peak, then it might not affect trains going into service, but may affect
trains due to stable there. The nature of the derailment - e.g. how long
it takes to clear - would also have an impact on the length of time the
service was affected. Because depot movements are no more than 5-10mph, a
derailment usually just means that a bogie or two has come off the rails
and needs the heavy gang to put the train back on the rails. There may be
damage to the train or track and once again the nature of this will have
an impact on how long it is before normal depot movements can be resumed.

A signal/points failure could have a similar effect on preventing trains
entering service/stabling, although this would normally be cleared up much
quicker and have a less overall impact on the service.

The derailment in Morden depot this morning meant that no trains could be
stabled at Morden after the morning peak and so were stabled elsewhere
along the line. As a consequence, various trains were cancelled ex depot
for this afternoon's peak.

Roger