On Wed, 8 Jun 2005, Paul Corfield wrote:

On Tue, 7 Jun 2005 17:58:32 +0100, Tom Anderson
wrote:

Why on earth was a train allowed to enter a section of tunnel leading
to points which were known to be broken, with three trains ahead of it?

The points at Marble Arch would have been "scotched and clipped" to fix
them in the appropriate direction (i.e. for the normal line running and
not the siding). Once this was confirmed the trains then receive
instructions to move at normal speed as the line is automatically
operated. Once the first train started to move the system would then
progressively move the following trains and thus it is more than likely
that another train would end up between stations. The presumption would
be that "through running" had been restored. What no one expected was
that the points would be in the wrong position and then be clonked by
the first train through.

That's what i thought. The problem, i'd say, is that the presumption was
rather premature - it seems a little rash to declare the full restoration
of through running before any trains had actually managed to run through!

Thanks for the info, though.

Also, i'm not sure what was happening with trains further back than
Lancaster Gate, but it seems to me that it would have made sense to
bring the last train in the queue back to the station as soon as the
problem was detected. If it was resolved, it could have started going
forward again, and since the time to reach Marble Arch would have been
dominated by the time taken for the queue to empty, no time would have
been lost. If it had not, it would have made detraining that little bit
quicker, plus it would have given passengers the opportunity to leave
the train instead of waiting.

The queue in such a situation would be jam all the way back to White
City as that is the next nearest turning point.

So what happened on the day in question? We know the two trains which were
between Lancaster Gate and Marble Arch reversed and detrained, but where
did they go after that, and what happened to the trains between White City
and Lancaster Gate?

Reversing trains (i.e.back up the tunnel as opposed to crossing over to
the other line) is not a normal procedure and where there are
computerised systems they are normally set to detect reversible moves as
"illogical" and to take appropriate action to prevent such moves. As
Clive said you need to take special steps to prevent all other train
movements if you decide to reverse a train against its normal mode of
operation.

Very true.

tom

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