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[email protected] · May 20th 04, 10:59 AM posted to uk.transport.london

In article , (Roland
Perry) wrote:

In message , Clive D. W. Feather
writes
Alternate working requires a sufficiency of crossovers to switch
trains. The tube lines don't have these, in general.

A design fault, then.

There's also a problem with trainstops - they need to be lowered to
prevent a train running the wrong way from "back-tripping". Except
where bidirectional working is allowed (e.g. at termini) this isn't
designed into the signalling.

Another fault.

[These are excusable when the tubes were originally designed for normal
working hours. I think we forget how little of life was 24x7 as
recently as 30 years ago. I could certainly drive from Cambridge to
Chelmsford at midnight and see no other car on the road. At some point
this changed radically - perhaps the tubes need to keep up.]
--
Roland Perry

This will gradually change when new signalling systems come in, although
the shortage of crossovers will be the restriction. Come movable block
(joint) signalling, trains will just be able to reverse wherever they are
and go back the other way - a sort of signalled wrong direction movement.
Ideal during one unders, security alerts etc.

Roger