"TheOneKEA" wrote in message
om...
I looked at the signalling diagram for the LW and LX sites and
it makes no mention of a west-facing single-aspect signal at Ongar;
only LX21, the two-aspect station starter, and an FRL, are shown.
Does anyone have any more information?

The signal approaching Ongar was a fixed yellow, designed to act as a
repeater for the red lamps at the end of the line. This arrangements was/is
not unique on LU - I think there is a fixed yellow approaching Chesham, and
also most tunnel sidings have sequences of them. Most are un-numbered,
however the one at Ongar was unique in that it's ident was "ONGAR".

I would guess it was installed as part of the post-Moorgate enhancements.
Most termini would have the last signal held at red until the train was
proved to have slowed, but presumably other arrangements were necessary at
Ongar because there weren't any approach signals. Obviously the yellow
isn't going to stop a fast-approaching train, but it would provide
protection at night if a driver couldn't see the landmarks where he had to
start braking for the terminus.