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| Re: AHB Level crossing timings 26/04/2012 at 10:15 #31837 | |
Stephen Fulcher
2027 posts |
I would imagine that a report of a wrong side failure from an S&T Technician would be taken with more credibility than a similar report from a random member of the public.
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| Re: AHB Level crossing timings 26/04/2012 at 14:08 #31847 | |
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GB
64 posts |
There was supposedly a problem with one of the AHB crossings on the Felixstowe branch this morning. A MOP rung the signaller stating a train had gone over the crossing with the barriers still in the air. Q the blokes in orange from Network Rail and after a lengthy investigation, train cancellations and delays and after speaking to the MOP again, it was revealed the MOP was mistaken and hadn't actually witnessed anything. Im not saying this is the same here but make sure you are certain you are correct before reporting it!! Log in to reply |
| Re: AHB Level crossing timings 26/04/2012 at 15:13 #31851 | |
jc92
3631 posts |
" said:There was supposedly a problem with one of the AHB crossings on the Felixstowe branch this morning. A MOP rung the signaller stating a train had gone over the crossing with the barriers still in the air. Q the blokes in orange from Network Rail and after a lengthy investigation, train cancellations and delays and after speaking to the MOP again, it was revealed the MOP was mistaken and hadn't actually witnessed anything. " said: Im not saying this is the same here but make sure you are certain you are correct before reporting it!!i experienced a similar situation at doncaster recently. the signal on the down main at the north ned of the station (i dont remember the ID) was only illuminating 3 out of 5 feathers (minimum acceptable amount before the feather fails to prove and the signal is held at red), however i felt no inclination to get involved in something that a) would require a proffessional opinion, B) something a driver, or station staff would pick up on and report via the correct channels, C) potentially cause more hassle than its worth. " said: Im not saying this is the same here but make sure you are certain you are correct before reporting it!!ditto "We don't stop camborne wednesdays" Log in to reply |
| Re: AHB Level crossing timings 26/04/2012 at 16:59 #31857 | |
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Hugh Jampton
69 posts |
" said:Im not saying this is the same here but make sure you are certain you are correct before reporting it!!Fear not! I wo'n't be reporting anything without going back to double check. However, the answers in this thread have helped establish whether it is worth the effort so I'm glad I asked the question. Thanks, everyone, for your help. Log in to reply |
| Re: AHB Level crossing timings 26/04/2012 at 18:27 #31861 | |
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Late Turn
696 posts |
Just a couple of further related questions if I may, to satisfy my own curiosity! Apologies for tagging on the end of Hugh's thread, but it seems the best place to me. When in the sequence does the AHB indicator in the box go from 'raised' to 'working'? Is it as soon as the amber road light first illuminates, the red road lights start flashing or the barriers start lowering? On a double line, as Clive explains, the train first strikes in (a minimum of?) 10 seconds before the sequence starts (to prevent the barriers raising behind a train on the opposite line). Is there then a second treadle to start the actual crossing sequence, or does it just count to ten? Any knowledge appreciated  .
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| Re: AHB Level crossing timings 26/04/2012 at 19:24 #31863 | |
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GB
64 posts |
Not 100% sure but I think it changes to "working" once the barriers start lowering or once they are proved lowered.
Last edited: 26/04/2012 at 19:24 by GB Log in to reply |
| Re: AHB Level crossing timings 26/04/2012 at 22:01 #31867 | |
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Firefly
521 posts |
Quote:When in the sequence does the AHB indicator in the box go from 'raised' to 'working'? Is it as soon as the amber road light first illuminates, the red road lights start flashing or the barriers start lowering?It happens as soon as the Amber light illuminates. Quote: On a double line, as Clive explains, the train first strikes in (a minimum of?) 10 seconds before the sequence starts (to prevent the barriers raising behind a train on the opposite line). Is there then a second treadle to start the actual crossing sequence, or does it just count to ten?On modern crossings the treadles are placed at 37 seconds (plus equipment operation time) from the crossing and there's a 10 second timer which delays the start of the sequence. older installations (Pre 1980) used to have the normal strike in point at 37 seconds and an ATC Strike in point at 52 seconds (another train coming). These installations had separate treadles at each strike in point. The following briefing note gives some details:- Quote: The working party report of 1979 relaxed many of the stringent measures imposed after Hixon and formed the basis for current level crossing protection. Major changes included a reduction in strike-in times and changes to timing sequences, removal of the neon ‘ATC’ signs, single means of strike-in initiation, facility to use AOCL (formerly OCFL) on double lines, and introduction of AOCR. Signing arrangements were also altered. Strike- in treadles were no longer required, except where there was evidence of track circuit shunting problems. Bi-directional controls were introduced for double line crossings with a consequent need for time releases for the track circuit stick control circuits. A complete new set of typical circuits was issued to accompany these changes. Last edited: 26/04/2012 at 22:03 by Firefly Log in to reply |
| Re: AHB Level crossing timings 26/04/2012 at 22:11 #31868 | |
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Stephen Fulcher
2027 posts |
And of course History goes full circles because now you have strike in treadles everywhere again!!
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| Re: AHB Level crossing timings 27/04/2012 at 06:21 #31872 | |
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clive
2738 posts |
" said:When in the sequence does the AHB indicator in the box go from 'raised' to 'working'? Is it as soon as the amber road light first illuminates, the red road lights start flashing or the barriers start lowering?The logic in the core code illuminates the WKG lamp if any of:
Quote: On a double line, as Clive explains, the train first strikes in (a minimum of?) 10 seconds before the sequence starts (to prevent the barriers raising behind a train on the opposite line). Is there then a second treadle to start the actual crossing sequence, or does it just count to ten? The core code just counts to 10. The core code was written after I had a chance to examine typical circuits (in the IRSE "Red Book", if anyone cares). They don't simulate those circuits relay by relay, but they do emulate the same internal states, so should have the same effect as real life. Log in to reply |
| Re: AHB Level crossing timings 27/04/2012 at 07:28 #31875 | |
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Firefly
521 posts |
Quote:And of course History goes full circles because now you have strike in treadles everywhere again!Yep, and this came about in the early 90's Quote: Note: national policy is now to have two treadles to assist each track circuit operation, but this could be achieved by other means e.g. axle counters. Log in to reply |
| Re: AHB Level crossing timings 27/04/2012 at 08:59 #31880 | |
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Late Turn
696 posts |
Thanks to all for the comments, which have answered both questions for me .
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