Re: Most seriously congested station

On Mon, 31 Aug 2009 07:10:09 +0100 someone who may be Peter
<REPLACEWITHMYFORENAME@xxxxxxxxxxxxxxxx> wrote this:-

Apparently calling on into the down through platform
is not permitted. Cardiff Central just about works because calling on
is routinely used.

Please excuse my ignorance, but what's "calling on", and how does this
help? I understood the first sentence of this paragraph, but not the
other two.

Calling on allows two or more trains into the section between
signals. Typically at a large station there is a signal near the
entrance to a platform and a signal at the exit and normally there
can only be one train between signals, so there can only be one
train at the platform at any time. Given that many platforms can
hold 10+ coaches and many trains are toy two coach trains this means
a lot of wasted platform. With more intensive services there could
be one train taking up a tiny part of the platform and one or two
trains waiting outside.

A main signal showing a proceed aspect tells the driver that the
line is clear up to and a little beyond the next main signal [1]. If
there is to be more than one train between the signals then a
special signal is needed, which tells the driver of this special
situation so that they can travel slowly enough to stop short of
other trains. The main aspect remains at danger to reinforce the
message.

The Railway Inspectorate had a downer on calling on for a while and
it was withdrawn in a number of places. I suspect that they would
have preferred to withdraw it altogether, but that would not be
practical. There is the occasional crash with calling on, but
usually nothing serious.


[1] with an exception, when the signal leads to buffer stops.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54
.

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