St Margarets station level crossing & signals

[KEVIN SMITH]

Hi When the Hertford east line was resignalled about 8 years ? the level crossing at St margrets station seemed to gain two signals to protect it on up line. There is a four aspect starter at the platform end (which had to be altered a couple of times before it was brought into use it ended up on a short post) and a three aspect signal just a short way before the platform ramp sorry I do not have have the signal numbers now but I could get them. There is not enough braking distance between them but when the barriers go down all signals go to green can anyone explain can anyone explain any of this ? please.

[rower40]

Closing-up signal L1240 at approach to platform. Its overlap extends to the platform starter L1238. Previous signal back from L1240 is L1242, "standard" 3-aspect sequence between L1242 and L1240, with no interaction with the level crossing to get a yellow on L1242. Next signal after L1238 is L1236, which protects Cranbourne MSL crossing.

St Margarets Level crossing has to be down and crossing-clear to get a proceed aspect in both L1240 and L1238. If L1238 is at danger, then L1240 becomes severely approach-controlled, AND still needs the level crossing down. For L1238 to clear, either L1236 must be off (reading over the MSL crossing), or train must be in the St Margarets platform.

So (as I understand it) the purpose of the closing-up signal L1240 is to allow a train to approach (but not enter) the station with the crossing still open to road traffic; the train may pass L1242 on yellow, and be prepared to stop just short of the station, while the barriers are still in the air. As the train slows to signal L1240, the crossing closes, and the train can then creep into the station to perform station duties, on green signals.

[StevieG]

" .... the train may pass L1242 on yellow, and be prepared to stop just short of the station, while the barriers are still in the air. As the train slows to signal L1240, the crossing closes, and the train can then creep into the station to perform station duties, on green signals. "

I don't know the setup at St. Margarets, but from rower40's clear description, I would imagine that (unless 1240 requires 1238 'Off' in all circumstances), there's probably also a scenario where, once the crossing is closed to road, if there is any reason that platform starter L1238 is incapable of clearing or is deliberately being held at red, then provided that 1238's overlap is clear, the approach release of L1240 would be to yellow only.
This would also allow the train into the station, before, on completion of station duties, it becomes detained by L1238 being at 'Danger', necessitating the driver to report this to the signaller.
If the train is not then to proceed, there could then probably be the ability, after any route/crossing timeout(s) have operated, for the crossing to re-open to road.

[ Edited twice; a few tweaks of wording, and additional content; 09:31 and 10:43 Sat. 02-May-2015.]