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| Emergency replacement switch defeats approach locking? 26/03/2017 at 18:11 #94125 | |
Hawk777
386 posts |
I noticed this in the King’s Cross sim, but I posted it here as I suspect it may be a common thing and not a sim-specific thing. KX appears to be equipped with comprehensive approach locking, at least on some of the territory. I was playing around with the down fast near Oakleigh Park when I discovered this phenomenon. In this area, four-aspect signalling is used, and there is a sequence of signals 495 (automatic with emergency replacement switch), 503 (automatic without emergency replacement switch), and 507 (controlled, protecting some pointwork). If you have a route set from 507 onwards and no circuits in the area are occupied, cancelling 507 drops the route immediately due to comprehensive approach locking. Makes sense. If you have a route set from 507 onwards and circuit TBSB, the one in rear of 495, is occupied, cancelling 507 provokes an approach locking timeout. This makes sense. Although 495 only drops from green to double yellow, so the resulting aspect sequence isn’t impossible, the driver of a train in TBSB might already have looked at 495 and seen it to be green. In that case the next warning (s)he would get would be 503 at single yellow, which is bad. However, if you have a route set from 507 onwards and circuit TBSB is occupied, you can hit the emergency replacement switch on 495, then cancel the route from 507, and the route drops immediately. You can then of course deactivate the emergency replacement on 495, leaving the aspect sequence exactly the same as I described in the previous paragraph, except that no approach locking timeout happened and you can adjust the points or set conflicting routes freely. Is this prototypical? It seems like a rather nasty omission from the interlocking systems if it is! Log in to reply |
| Emergency replacement switch defeats approach locking? 27/03/2017 at 11:05 #94144 | |
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kbarber
1743 posts |
I may be wrong, but - unless that interlocking has been replaced (and I know some of them have been, notably Finsbury Park and Hitchin/Stevenage/Langley Jc) - I have an idea KX didn't have comprehensive approach locking (economy being an issue at the time it was built). Of course, if there were comprehensive approach locking that would seem to be a bit of a hole in the locking. I'd have thought approach locking took effect as soon as a relevant TC became occupied and irrespective of changes of state of signals in rear. (Perhaps one of our S&T members would confirm?) Last edited: 27/03/2017 at 11:08 by kbarber Reason: Add 2nd para Log in to reply |
| Emergency replacement switch defeats approach locking? 29/03/2017 at 03:38 #94198 | |
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Hawk777
386 posts |
kbarber in post 94144 said:I may be wrong, but - unless that interlocking has been replaced (and I know some of them have been, notably Finsbury Park and Hitchin/Stevenage/Langley Jc) - I have an idea KX didn't have comprehensive approach locking (economy being an issue at the time it was built).Ah, well it does in SimSig  I didn’t choose KX specifically for any reason; I didn’t even know whether it was comprehensive or not in real life.kbarber in post 94144 said: Of course, if there were comprehensive approach locking that would seem to be a bit of a hole in the locking. I'd have thought approach locking took effect as soon as a relevant TC became occupied and irrespective of changes of state of signals in rear. (Perhaps one of our S&T members would confirm?)Right, I would expect that it shouldn’t care about aspects at all, other than its own; any red signal in rear would certainly mean that comprehensive approach locking needn’t look further back, but that having been said, any red signal would also be either held at red by an occupied TC (in which case that TC ought to require approach locking timeout anyway), or be controlled without a route set (in which case the lack of route is more relevant than the signal aspect), or be an emergency replaced automatic (in which case that shouldn’t change anything). Which means actually checking the aspects shouldn’t be necessary, I would have thought? Log in to reply |
| Emergency replacement switch defeats approach locking? 29/03/2017 at 03:58 #94200 | |
GeoffM
6377 posts |
I vaguely thought I'd fixed this a while ago but obviously not. Mantis 17150 for me to do, though it's not as trivial to fix as it might sound. Thanks.
SimSig Boss Last edited: 29/03/2017 at 03:58 by GeoffM Reason: . Log in to reply |
| Emergency replacement switch defeats approach locking? 30/03/2017 at 05:07 #94217 | |
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Hawk777
386 posts |
Thanks Geoff. I certainly wouldn’t call it high priority
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