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| Understanding warner routes better 27/04/2014 at 13:11 #59613 | |
Peter Bennet
5360 posts |
" said:Had a quick re-read of the thread but I don't think it's been mentioned that reduced overlap/warner routes exist without yellow warner exit buttons. Birmingham International platforms 1 and 2 on the New Street is an example and Weston-Super-Mare and Clifton Down on Bristol also come to mind. There are more than likely others.Post 13 was supposed to refer to them. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Understanding warner routes better 27/04/2014 at 14:33 #59614 | |
Stephen Fulcher
2025 posts |
Just to throw a spanner in the works, Western Region E10k interlocking has the concept of "delayed yellow", which although similar in operation to warner routes is not quite the same. You can step back down again, and to select them generally involves keying a set of points in the standard overlap distance against the route, rather than individual route selection. As a signalman, you would have to be careful not to cause a change of aspect by keying a set of points in an overlap and causing the signal to revert to delayed yellow from the full overlap. Weston Super Mare on Bristol is simulated more-or-less like this, and I suspect Clifton Down is the same. The only thing SimSig doesn't replicate is the automatic stepping down of a route. Log in to reply |
| Understanding warner routes better 29/04/2014 at 11:36 #59727 | |
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kbarber
1712 posts |
Yet again I wonder if it would help to go back to mechanical/AB principles? Until the Abbots Ripton collision of 1876, there was no requirement for any margin to be clear beyond a stop signal before a second train was permitted to approach it. The Inspecting Officer's report made great play of the fact that the distance the AB system then maintained between trains might be 'no more than the thickness of a signal post' (paraphrase). As a result it became a requirement that each signalbox had a 'clearing point', a distance beyond the first stop signal that must be clear before a train could be accepted from the rear and must remain clear until the approaching train had either passed or come to a stand. That distance was standardised at 1/4 mile (440 yards or 402 metres). Remember continuous brakes were by no means universal, even on passenger trains, so there was quite a high possibility of trains overrunning signals at danger as a result of minor misjudgements. Even when continuous brakes became a requirement for passenger trains (Regulation of Railways Act 1889), unbraked freight trains remained a feature of UK operations that wasn't finally abolished for another 100 years - well in to the period of many SimSig schemes! As you can imagine, keeping 1/4 mile clear was pretty restrictive at times. So provision was made by means of AB Regulation 5 ('where specially authorised'  for a reduction of the clearing point under certain circumstances. There were usually limitations on when it could be done ('in clear weather' was very common) and on the classes of train affected (again a common one was 'for trains not conveying passengers provided the clearing point is not occupied by a train conveying passengers'). Authority would be given in the SBSIs. Drivers had no specific information regarding where Reg 5 was authorised (a real defect, in my view) - they just had to learn it by experience. The procedure was that, when a train was offered (and provided it complied with the authorisation), the advanced signalman would respond with the 'warning acceptance' bell code (3 pause 5 pause 5 beats on the bell, sometimes described as 'section clear but station or junction blocked'). When the offering signalman had repeated it back, line clear would be given. The offering (rear) signalman had then to keep his section signal at danger and drop the approaching train down to the box signal by signal, then display a green handsignal outside the box; when the driver acknowledged it with a blast on the whistle, he could clear the remainder of his signals. Yes, it was a faff - and a big one - but it kept traffic moving (it was used many times a day between Junction Road and Gospel Oak). One little feature, laid down in the rule book, was that if a driver was starting away from a section signal having been brought completely to a stand he must consider the line clear to the home signal only - i. e. no clearing point - at the home signal of the next box. That provided for a Reg 5 acceptance after the train had already passed the box.Sometimes a warning signal - a small arm below the main arms - would be provided on the section signal. (At Acton Wells there was an IB in rear of the box - a very rare animal - that had a warning signal to allow trains to be drawn up to the home while a train was running to or from Acton Yard. As far as I reacall, there was no restriction on its use.) Some early power installations had a similar provision (remember many of them continued to be worked AB). The principle of a safety margin was carried over into TCB installations and therefore restricted overlaps also had to be provided for. Again, where it wasn't convenient for handsignalling, a subsidiary aspect of some kind would be provided. The LNER used an isolated 4-aspect signal in 3-aspect territory for similar purposes; a double yellow indicated a restricted overlap at the second signal ahead, while a green meant a full overlap at that same second signal (there were several of these in the 1935 installation at Hackney Downs, retained when the signalling was adapted for electrification in 1960 and indeed an additional one was provided at Clapton to indicate a restricted overlap at Coppermill Junction). But at some point the idea of a delayed yellow became the preferred option (replicating the AB instruction relating to starting away from a stand at a section signal). All that, of course, was quite separate from the matter of controlling these aspects. It was easy where the green handsignal was used. In mechanical days it was also easy where a separate warning signal was provided - a separate lever did the job. Likewise for a OCS or IFS panel. The LNER version was inherently automatic, of course (although I don't know whether it would step up & down according to the setting of points - all the instances at Hackney had junctions in the overlap). But something different had to be done where there was NX working. I have an idea manual swinging of points may have been the earliest approach, followed by automatic setting of a warner route which would then step up when the next route was set and the provision of a separate exit button as the final development, but I may well be wrong. (Does anyone know for certain?) Of course before VDU interfaces the warner exit was a separate button on the panel, which could easily be made distinguishable from the normal exit. (There was usually a bit more room to put them too, and more flexibility as they could be placed within platforms & such.) The BR IECC symbol is quite a neat, elegant solution. But as others have said it's much more about how to control something than about the form of the signal itself. It sometimes takes a bit of remembering that, in NX working, the exit button is part of the control for the signal in rear (and when it's acting as an exit has nothing at all to do with the signal it's actually adjacent to). All the more confusing as, in the vast majority of installations (WR turn-push panels the big exception) it can also act as an entrance for the signal it is adjacent to! Log in to reply The following users said thank you: Splodge, Firefly, maxand, AndyG, Forest Pines |
| Understanding warner routes better 29/04/2014 at 14:29 #59736 | |
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maxand
1637 posts |
Wonderful dissertation Keith! Quote: It sometimes takes a bit of remembering that, in NX working, the exit button is part of the control for the signal in rear (and when it's acting as an exit has nothing at all to do with the signal it's actually adjacent to). Nicely pointed out. Quote: All the more confusing as, in the vast majority of installations (WR turn-push panels the big exception) it can also act as an entrance for the signal it is adjacent to! Now that I didn't know. Haven't seen this happen in SimSig yet. Thanks. Last edited: 29/04/2014 at 14:31 by maxand Log in to reply |
| Understanding warner routes better 29/04/2014 at 15:18 #59739 | |
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kbarber
1712 posts |
" said:
Sorry Max, it happens all the time. Not with warner exits, but every time you set a main route you click on the exit (the next signal), then if there's another route you click again on the same spot (in a panel you'd push the same button a second time) and it's miraculously transformed itself into an entrance. The reason it doesn't happen with the WR (or any other) turn-push panels is that all the exits are buttons, usually just in rear of the turn switch that constitutes the next entrance. Log in to reply |
| Understanding warner routes better 30/04/2014 at 00:54 #59783 | |
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maxand
1637 posts |
Sorry if I misunderstood you. I thought you meant that a warner exit symbol (not the exit signal to which it refers) could be used as the entry signal for the next route segment.
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| Understanding warner routes better 30/04/2014 at 01:29 #59787 | |
GeoffM
6282 posts |
" said:Sorry if I misunderstood you. I thought you meant that a warner exit symbol (not the exit signal to which it refers) could be used as the entry signal for the next route segment.Some simulations have what are internally called "additional exits". These serve as an exit to a route where the signal is a long way away from the entrance, or - in the case of paged sims - on a different page. The by-product of this is that you can double-click on it, i.e. as an exit and then as entrance to the next route. As per IECC of course. :cheer: (Brighton has five, each for the wrong-road running. For example, click on the exit arrow just to the right of the Keymer Junction label, scroll to the right, and you'll see signal 423's entrance cursor near Preston Park flashing merrily away. SimSig Boss Last edited: 30/04/2014 at 01:32 by GeoffM Reason: Example added Log in to reply |