On Jan 6, 1:52*pm, wrote:
1) the depot is at Cockfosters. Not sure what time this incident took
place, but if the train died in a place where it blocked or

MId to late afternoon.

OK, so depot isn't a major issue.

significantly impaired depot access, then that's going to have an
obvious knock-on effect on the line

The knock on effects were caused (as usual), by terminators sitting at
arnos grove for ages before being sent back down the line. The concept
of stepping back seems to be a foreign one to the piccadilly line and
its staff.

Indeed, it might be good to implement stepping back for emergency
reversals. And it's possible that it hasn't been put into place
because nobody cares about getting things going, or because of union
grumpery.

However, it's also possible that it hasn't been implemented because if
the line's in turmoil and all the trains (with drivers on board,
obviously) are stuck behind each other in tunnels along the route,
where exactly are you going to get hold of the extra spare drivers to
run the service? Do they sit around drinking tea at Arnos 29 days a
month just in case things go wrong? Presumably you need another chap
drinking tea at Northfields, and another at Hyde Park Corner, to cope
for failures at those locations...

2) normal line operation is based on turning some trains at Arnos
extremely expensive redundancy (in this case, adding signalling and
track work at Arnos so that it can be used as a full-capacity terminus

Its already got it. All it needs is for the staff to put some effort
into being ready for their train when it arrives and the signaller to
switch the route quickly.

I don't think that's true. The track layout at CULG implies that the
through platforms aren't reversible:
http://www.davros.org/rail/culg/piccadilly.html#layout
....giving you 1 reverser at a time instead of 3 at Cockfosters.

Arnos was a terminus anyway for a while
until the section to cockfosters was completed.

True, but I imagine they changed the signalling at the point when the
extension opened.

mirroring Cockfosters, or turning one of the stations north of Arnos
into an alternative reversing point - in either case, these will only

There is one - its called Oakwood.

No, that's a plain-track station with no reversing facilities. Trains
that are advertised as Oakwood terminators are going into the depot
(where they can be reversed, but complicatedly and slowly because
that's not what it's intended for).

--
John Band
john at johnband dot org
www.johnband.org