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| Track circuited AB sections 29/05/2013 at 22:56 #45268 | |
Steamer
3984 posts 
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I've just been reading the North Wales Coast manual, and it says that some of the AB sections (for example the Down Main from Abergele to Llandudno Junction) are track circuited throughout. In these cases, what is the purpose of the block instruments? If train detection is available throughout the section, doesn't it essentially become TCB?
"Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |
| Track circuited AB sections 29/05/2013 at 23:03 #45269 | |
headshot119
4869 posts |
However when Abergele switches out, train detection isn't available from Rhyl all the way through to Llandudno Junction, perhaps a reason for it being left as AB. It's mainly provided on the sections leading to Llandudno Junction, and this allows the signaler to give train out of section to the adjacent box before seeing the tail lamp. On a different note I know a signaler who used to work in Abergele before the track circuits where replaced by axle counters, apparently the rain was always dreaded as it used to drop one of the track circuits on a regular basis meaning they couldn't switch out and go home. "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply The following user said thank you: Steamer |
| Track circuited AB sections 29/05/2013 at 23:05 #45270 | |
UKTrainMan
1803 posts |
Don't quote me on this.... but I believe it was something originally introduced with the first release of Central Scotland (the free version), and was introduced as an option to make it slightly easier for those players who wished to utilise it to assist them. Post composed before 'headshot119' had posted Any views and / or opinions expressed by myself are from me personally and do not represent those of any company I either work for or am a consultant for. Last edited: 29/05/2013 at 23:07 by UKTrainMan Reason: adding 'disclaimer' Log in to reply |
| Track circuited AB sections 29/05/2013 at 23:11 #45272 | |
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Late Turn
699 posts |
I can think of a fair few AB sections that are track-circuited throughout. It's not uncommon with short sections, where the berth track circuit for the box in advance extends back to the section signal in rear (Rothley - Swithland in both directions on the preserved GCR being the first example to spring to mind). On longer sections, it could be to enable the chap in advance to send TOS without seeing a tail lamp, if the circumstances required that. A section TC'd throughout doesn't automatically become TCB. One significant difference is the lack of ability (unless slots of some sort are provided) for the chap at the advance end of the section to refuse a train on TCB, which could be necessary if there are connections immediately beyond the home signal. I think there is, or has been at some point, a requirement for the line in either direction through a section to be signalled by the same method (although I can think of at least one significant exception!). Halifax - Mill Lane (Bradford) seems to be a good example of both of these, with the AB/TCB fringe some miles from Mill Lane! Tom Log in to reply The following user said thank you: Steamer |
| Track circuited AB sections 29/05/2013 at 23:27 #45273 | |
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Steamer
3984 posts
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headshot119 said:However when Abergele switches out, train detection isn't available from Rhyl all the way through to Llandudno Junction, perhaps a reason for it being left as AB.If Abergele switches out, does the AB section extend through Colwyn Bay to Llandudno Junction then, since if the train were to be divided between Rhyl and Abergele there'd be no way to detect it? "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |
| Track circuited AB sections 29/05/2013 at 23:54 #45274 | |
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Late Turn
699 posts |
The AB section would still end at LJ's home signal, as that's what the definition of an AB section states. However, as the section through from Rhyl wouldn't then be TC'd throughout, the chap at LJ wouldn't be able to give TOS until either he'd seen the tail lamp, or the traincrew advised him that it had left the section complete.
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| Track circuited AB sections 30/05/2013 at 02:14 #45279 | |
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Danny252
1461 posts |
" said:I can think of a fair few AB sections that are track-circuited throughout. It's not uncommon with short sectionsI think the vast majority of (track-circuited) stations with more than one signal box fell into this category, for one. Log in to reply |
| Track circuited AB sections 30/05/2013 at 06:43 #45280 | |
jc92
3685 posts |
" said:t some of the AB sections (for example the Down Main from Abergele to Llandudno Junction) are track circuited throughout. In these cases, what is the purpose of the block instruments? If train detection is available throughout the section, doesn't it essentially become TCB?Ive asked this question before, and one reason is clearing points and manually operated points. if an overlap extends over a set of points, they have to set and detect before it will clear, however if they are operated by the box in advance, this setup isnt possible, hence offering a train, and it being accepted when the box in advance has a safe overlap. York PSB worked absolute block to Burton Lane SB for this reason in the scarboro direction, but in the other direction, the working was TCB. "We don't stop camborne wednesdays" Log in to reply The following user said thank you: Steamer |
| Track circuited AB sections 30/05/2013 at 08:38 #45282 | |
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kbarber
1742 posts |
" said:I think there is, or has been at some point, a requirement for the line in either direction through a section to be signalled by the same method (although I can think of at least one significant exception!). If 'twas so it certainly didn't apply in the early 1960s, date when the down fast from Arlesey to Biggleswade (formerly B'wade South) became TCB while the up fast remained AB (but with 'home', 'starter' and 'IBH' as 3-aspect signals spaced at regular intervals so to the driver it looked like standard 3-aspect TCB)! Log in to reply |
| Track circuited AB sections 30/05/2013 at 08:55 #45283 | |
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kbarber
1742 posts |
Track circuits throughout were essential if an IBH was provided in rear of the box. The North london line had a number of these. Acton Wells had one at Friars Place (on the up from Acton Central); as well as the stop arm it had the splitting distant for Acton Wells itself and a subsidiary (warning) arm to allow a train to approach while the junction to/from the WR was in use. (I have a suspicion this was why an IB in rear was chosen, I imagine before Friars Place box was closed - in the 1930s I suspect - Regulation 5 was authorised but of course you can't do Reg 5 with an IB in advance. The fog signalling arrangements were the means by which some spectacularly loose working could be achieved - I've posted in an earlier thread about 'Sunday Block' at Acton Wells.) Camden Road and Dalston Western Junction also had them, in both cases with conventional IBs in advance as well, as a way of abolishing a whole series of boxes while keeping the short sections necessary to work a very intense traffic. During the stageworks for West Hampstead PSB there was at least one box (Finchley Road) that was provided with track circuits throughout from the box in rear (Cricklewood); this allowed the abolition of West Hampstead, with 3-aspect signals being provided somewhere in the vicinity of the erstwhile Watling Street Junction (abolished a couple of years before, resulting in a longish section from Cricklewood to West Hampstead) and at the London End of West Hampstead platforms (putting the junction at Finchley Road way beyond the overlap and thus freeing up the working there quite considerably). The 4-aspect starter was retained, and with 3-aspect signals installed at Cricklewood South Junction (at the same time Watling St was abolished) meant mas effectively started there rather than at Carlton Road. Train out of Section could be given as soon as the overlap TCs of the outermost signals were clear but the signalbox instructions required that 6 bells be sent if the train susequently passed without tail lamp. Log in to reply The following user said thank you: Steamer |
| Track circuited AB sections 30/05/2013 at 08:58 #45284 | |
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Stephen Fulcher
2078 posts
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There is a telephone provided at Colwyn Bay for the train crew to contact Llandudno Junction Signal Box to confirm that they have arrived complete for situations where this is required, such as Abergele being switched out, or an Axle Counter failure. Another example I can think of is Truro and Par work Absolute Block to each other between Probus and Truro. The Down line is not track circuited as the train will pass Truro Signal Box half a mile after passing the outermost home signal (T50) so the Signalman can observe the tail lamp, but the Up line is an axle counter section to enable the Signalman at Par to give out of section as soon as the train passes beyond the overlap of PR112 signal at Probus, even though it is still fifteen to twenty minutes before he will personally see the train. EDIT: Looking at the photos Andrew G posted here some time ago, it would seem that sighting a tail lamp out of Llandudno Junction box might be difficult due to few windows. Last edited: 30/05/2013 at 09:02 by Stephen Fulcher Log in to reply The following users said thank you: Steamer, headshot119 |
| Track circuited AB sections 30/05/2013 at 10:46 #45287 | |
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Late Turn
699 posts |
" said:" said:I think there is, or has been at some point, a requirement for the line in either direction through a section to be signalled by the same method (although I can think of at least one significant exception!). It equally didn't apply more recently when the Down line(s) - not sure whether it was before or after the Down Goods was reinstated - between Brocklesby and Barnetby became TCB, with the Up Main remaining AB with a (conventional!) IB section. In the case of Halifax - Mill Lane, there's a sensible explanation for the section towards Halifax being AB (connections immediately in advance of the home signal, with a long tunnel not far in rear!), but no such explanation for the opposite direction, with AB fringing to Mill Lane's TCB in the middle of nowhere some miles from Mill Lane itself! Log in to reply |
| Track circuited AB sections 30/05/2013 at 16:24 #45295 | |
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vontrapp
210 posts |
Stockport is fully TC'd and yet AB.
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