DavidBird Posted November 21, 2012 Share Posted November 21, 2012 In this situation to allow a train from the Up main into the siding, the sub on TT 348 will clear with a "SDG" indication on the stencil. 1) Does the siding have to be clear up to a certain point, or will the signal clear just with the correct route set up? 2) If so, is this point marked in any way, by a lineside notice, or even a set of trappoints? 3) Does this point also mark the limit for internal shunting movements, or would that be allowed right up to TT 351? Thanks Link to post Share on other sites More sharing options...
RMweb Gold beast66606 Posted November 21, 2012 RMweb Gold Share Posted November 21, 2012 The track circuit would finish at TrenT 351 signal with a berth to detect a vehicle standing at the signal as this is a locally controlled shunt move the siding could be seen to be clear by whoever was operating the shunt frame, elsewhere there would be local instructions to cover anything special but generally down to the driver to make sure it's clear as far as they need to go, and the box and control would know what was already in there so they wouldn't try and send three trains into a single dead end siding for example. Link to post Share on other sites More sharing options...
RMweb Gold PaulRhB Posted November 21, 2012 RMweb Gold Share Posted November 21, 2012 Beasts info is bang on as expected I see it's an ordnance depot so taking Marchwood MOD as an example the arrangement in the instructions is that in advance of the train arriving the Signalman gets permission from the MOD shunter for the train to approach the security gates. He can then clear the signal towards the gate. Coming out is the reverse, the MOD ask permission for the train to approach the signal. In each case it means you don't get two trains heading towards each other on the siding. The telephone allows the driver to contact the signalman if he has to be detained on the exit signal. Some yards had and have shunt 'spots' where the shunter had a switch that had to be turned to release the interlocking and allow the signal to be cleared to enter the yard too. This again is to stop conflicting movements as the Shunter has total control of the yard. With a siding under the Signalmans sole control it's up to them to record what's in there and make sure there's room before sending another in. We use engraved tags on the diagram to record them and act as reminders. Link to post Share on other sites More sharing options...
DavidBird Posted November 21, 2012 Author Share Posted November 21, 2012 The track circuit would finish at TrenT 351 signal with a berth to detect a vehicle standing at the signal So the sub signal would clear as long as there was nothing actually standing at 351. Thanks, that answers the question. as this is a locally controlled shunt move the siding could be seen to be clear by whoever was operating the shunt frame,... In this case the shunt was still controlled by Trent PSB, although the former signal box at Attenborough was named "Attenborough Shunting Frame" it only controlled the level crossing. Link to post Share on other sites More sharing options...
RMweb Gold PaulRhB Posted November 21, 2012 RMweb Gold Share Posted November 21, 2012 So the sub signal would clear as long as there was nothing actually standing at 351. Not necessarily as sidings are permissive working I suspect the track is for indication rather than interlocking. It may be interlocked so that the track has to be occupied to clear the exit signal in some cases too just to control speed down. It depends on how they intended to operate that siding which you'd need one of the Signalmen or the special box instructions to know. Link to post Share on other sites More sharing options...
Grovenor Posted November 21, 2012 Share Posted November 21, 2012 See http://www.norgrove.me.uk/signalling/plans/trent.gif There was no berth track for 351 as built, unless one has been added since, the controls on 348 shunt, excluding any approach control, would just be the points set and locked, tracks clear over the points and 351 at stop and free of approach locking. Regards Keith Link to post Share on other sites More sharing options...
Edwin_m Posted November 21, 2012 Share Posted November 21, 2012 So the sub signal would clear as long as there was nothing actually standing at 351. Thanks, that answers the question. No, the track circuit would almost certainly finish just next to the signal post so anything beyond would not be detected. There is probably nothing in the signalling to stop a train being sent in when there is something already standing at the signal. (Edit: Grovenor has confirmed that is the case here). From a safety point of view this is managed by the rule that on passing a subsidiary aspect the train must be driven slowly enough to stop short of any obstruction. Obviously though it's not a direct safety issue having two trains nose to nose in the siding is not helpful (and sorting it out leads to unsignalled moves etc which increase the risk of something else happening). Hence the need for the signalman to be sure that the siding is clear and ready to accept the train before signalling it in. The track circuit going up to the signal is probably the same one as on the adjacent main line, so if a train in the siding passes the signal at danger the protecting signal on the main line (TT349 and possibly also TT355 depending on exact positions) would go back to red. There will be a device called a track circuit interrupter which maintains the track circuit occupied if something goes through the trap points, so the protecting signal remains at danger even if whatever passed the signal has now rolled off the end of the rails. Link to post Share on other sites More sharing options...
Grovenor Posted November 21, 2012 Share Posted November 21, 2012 The track circuit going up to the signal is probably the same one as on the adjacent main line, so if a train in the siding passes the signal at danger the protecting signal on the main line (TT349 and possibly also TT355 depending on exact positions) would go back to red. There will be a device called a track circuit interrupter which maintains the track circuit occupied if something goes through the trap points, so the protecting signal remains at danger even if whatever passed the signal has now rolled off the end of the rails. All of which can be seen on the numbering plan I linked to. Unusually there is no GPL to allow trains to reverse into the siding so there must be run round facilities inside, in such a case the plan would usually say sidings rather than siding and would not show an end of track marker. (See elsewhere on plan). Regards Keith Link to post Share on other sites More sharing options...
DavidBird Posted November 21, 2012 Author Share Posted November 21, 2012 Thanks to you all. As always, the replies exceed expectations! Especially thanks to Keith for the link to the plan of Trent, now gives me the individual turnout numbers. Link to post Share on other sites More sharing options...
micknich2003 Posted November 22, 2012 Share Posted November 22, 2012 As we say localy, "Sub to Sub, or Sub to Destruction", in other words, stop short of any obstruction. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.