In article ,
Tom Anderson writes
However, (a) trains
would have to slow down for the station starter anyway (no idea what that
means!)

The station starter is the signal at the departure end of the platform;
while it is red, the train can't (legally) start away.

On LU the signalling is designed on the assumption that all trains will
be stopping at every station[*]. If a train runs through a station at
speed and passes a red signal, it is possible that the trip stops will
not stop it in time to prevent an accident [+]. Therefore drivers are
instructed to slow to 5mph (or in some places 10mph) when running
non-stop through a station.
[*] There are some specific exceptions, such as Turnham Green on the
Piccadilly, and the signalling in these places is altered accordingly.

[+] In general, a signal can only turn green if a train hitting the
train stop of the following red signal *at line speed* will be stopped
before the point of actual danger (e.g. another train). Designing for
the maximum possible speed of all trains would be unduly restrictive, so
designing to the speed limit of the line is a sensible compromise.

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