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| Throwing points in Overlap 06/08/2010 at 23:42 #1580 | |
Danny252
1461 posts |
This one's been bugging me for a few days! In Simsig, it's perfectly legal to throw a set of points inside an overlap with a train approaching. However, in the case of a train overrunning a signal, this could mean that the points are changing as a train runs over them. In mechanical signalling, it would be a suspendable offence to change points in a clearing point (the equivalent of an overlap) - is it no longer the case that the overlap has to be set and locked until the train has passed/stopped/etc? Log in to reply |
| Throwing points in Overlap 06/08/2010 at 23:42 #10540 | |
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Danny252
1461 posts |
This one's been bugging me for a few days! In Simsig, it's perfectly legal to throw a set of points inside an overlap with a train approaching. However, in the case of a train overrunning a signal, this could mean that the points are changing as a train runs over them. In mechanical signalling, it would be a suspendable offence to change points in a clearing point (the equivalent of an overlap) - is it no longer the case that the overlap has to be set and locked until the train has passed/stopped/etc? Log in to reply |
| Throwing points in Overlap 06/08/2010 at 23:54 #10541 | |
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UKTrainMan
1803 posts |
I think the overlap will lock in it's current position after the train has passed the point at which swinging the points into any other position would be too risky, i.e: points would take too long to swing before the train reaches or potentially fails to stop at the signal. As I and many others generally consider SimSig to be highly accurate of 'The Real Thing' then I would assume that this is also the case for The Real Thing....although I don't know otherwise so don't take this as a final answer. Hope this helps. EDITED TO ADD; Danny252 said: However, in the case of a train overrunning a signal, this could mean that the points are changing as a train runs over them.SimSig does not simulate SPADs or any other incidents along those lines (fatalities, train crashes, level crossing accidents, etc, etc) and so for the points to be able to be swung with a train going over them would probably mean a bug with the simulation or a player not playing the simulation properly - although that said as soon as the train has entered the track circuit over the points then they'd automatically lock in their current position anyway. 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. Log in to reply |
| Throwing points in Overlap 07/08/2010 at 00:01 #10542 | |
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Danny252
1461 posts |
UKTrainMan said:I think the overlap will lock in it's current position after the train has passed the point at which swinging the points into any other position would be too risky, i.e: points would take too long to swing before the train reaches or potentially fails to stop at the signal.Just tested, it will swing even when the TC before the signal is occupied by a moving train. Log in to reply |
| Throwing points in Overlap 07/08/2010 at 00:05 #10543 | |
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UKTrainMan
1803 posts |
Danny252 said:Just tested, it will swing even when the TC before the signal is occupied by a moving train.May be location specific, i.e: depending on the gap between the signal and the points. Of course there is a very slight chance it could be a bug. 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. Log in to reply |
| Throwing points in Overlap 07/08/2010 at 05:58 #10544 | |
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Jsun
212 posts |
Following lengthy discussion on the signalbox forum I'm convinced that changing the points in advance of a train in the clearing point is legal provided the other clearing point is clear. In either event the points lock if a train SPADs or as a method of flank protection, other than that they will normal and reverse to your hearts content. Simsig does require the points in the overlap to prove before the signal in rear will clear, with the exception that points in the overlap need not prove if a mainroute in advance of the next signal is called, in this case the rear signal clears straight away.
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| Throwing points in Overlap 07/08/2010 at 10:07 #10547 | |
GeoffM
6281 posts |
IRL facing points in an overlap within 50 yards (figure varies around the country) are locked by the berth track becoming occupied, and are eventually unlocked at the same time as the overlap releases (or would release if the route is in auto). Facing points further away are free to move any time, subject to other conditions of course. This is simulated in SimSig but does require the developer to know that the point is close enough to require this time of operation locking. Sometimes it's obvious, other times it's borderline and without control tables or somebody (eg signaller) knowing and telling us, it's hard to guess for sure. One example is Bristol signal 24 (Bristol East Jn) - you won't be able to swing the points once a train hits the berth track until the overlap drops. As for points detected in the overlap, they're allowed 7-8 seconds to move before the signal will be replaced to danger. Again, simulated in SimSig. SimSig Boss Log in to reply |
| Throwing points in Overlap 07/08/2010 at 10:19 #10549 | |
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GeoffM
6281 posts |
http://www.rgsonline.co.uk/Railway_Group_Standards/Control%20Command%20and%20Signalling/Railway%20Group%20Standards/GKRT0060%20Iss%201.pdf section 5.2.8 (document is withdrawn but the principles are the same). It states 22yds rather than the 50yds I mentioned - perhaps it's changed over the years or I'm just remembering wrongly.
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| Throwing points in Overlap 07/08/2010 at 12:27 #10556 | |
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clive
2737 posts |
Apart from the case of "time of operation locking" that Geoff mentioned, it's permitted to swing the points in an overlap provided that the new overlap is also available, with all relevant points also having to be swung to the correct position as well. The risk from swinging overlaps only happens if the points fail mid-stroke *and* the approaching train is past the previous signal *and* the approaching train then SPADs. It's viewed that this risk is sufficiently small that the benefits of swinging overlaps far outweigh it. Log in to reply |
| Throwing points in Overlap 07/08/2010 at 19:58 #10559 | |
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Danny252
1461 posts |
clive said:The risk from swinging overlaps only happens if the points fail mid-stroke *and* the approaching train is past the previous signal *and* the approaching train then SPADs. It's viewed that this risk is sufficiently small that the benefits of swinging overlaps far outweigh it.Alright, fairly content with that - modern point motors are probably a wee bit more reliable than signalmen and mechanical points, and AWS/TWPS probably have a role to play in it. Log in to reply |
| Throwing points in Overlap 07/08/2010 at 21:26 #10564 | |
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kbarber
1711 posts 
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I think the rule in AB areas that Danny quoted was on the GW only (of course it might've been incorporated in modern instructions but I wouldn't know about those  ) In other regions it seems to have been permissible to move points within the clearing point (AB equivalent of overlap) provided it was safe to do so. I can think of places that would have been completely impossible to work were it not so.
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| Throwing points in Overlap 08/08/2010 at 11:13 #10567 | |
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davidt
13 posts |
GeoffM said:http://www.rgsonline.co.uk/Railway_Group_Standards/Control%20Command%20and%20Signalling/Railway%20Group%20Standards/GKRT0060%20Iss%201.pdf section 5.2.8 (document is withdrawn but the principles are the same).The current version of that document seems to be available at http://www.rgsonline.co.uk/Railway_Group_Standards/Control%20Command%20and%20Signalling/Railway%20Group%20Standards/GKRT0060%20Iss%204.pdf Log in to reply |
| Throwing points in Overlap 08/08/2010 at 14:58 #10572 | |
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Danny252
1461 posts |
kbarber said:I think the rule in AB areas that Danny quoted was on the GW only (of course it might've been incorporated in modern instructions but I wouldn't know about thoseWhilst I will admit my non-Western knowledge is somewhat limited, I do know that in the SVR Rulebook, based on BR Rules (which would have been an edition from the 1940s/50s, I forget the date), CPs are religiously adhered to there, and cannot be changed. Also, I've never heard of CPs being changable on the rest of the "Big Four". If CPs make it impossible to work, special CPs or Regulation 5 (no CPs, but driver must be forewarned) would probably be used. Log in to reply |
| Throwing points in Overlap 08/08/2010 at 15:45 #10581 | |
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kbarber
1711 posts
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Danny252 said:kbarber said:The Valley does indeed work to GW/WR Regs (right down to not answering 2-1, or at least it used to). Bewdley North has a specific exemption allowing No. 8 (? - I think - the facer from P1 to the Main) Xover to be swung after LC has been given to the South, provided TES hasn't been received.I think the rule in AB areas that Danny quoted was on the GW only (of course it might've been incorporated in modern instructions but I wouldn't know about thoseWhilst I will admit my non-Western knowledge is somewhat limited, I do know that in the SVR Rulebook, based on BR Rules (which would have been an edition from the 1940s/50s, I forget the date), CPs are religiously adhered to there, and cannot be changed. No such exemptions existed at places I knew in other regions (Reg 5 was normally used when a clearing point was blocked rather than when an alternative needed to be used and then swung). One I became very familiar with was Finchley Road (Midland), where the facing points in the Down Passenger were very close to the home. It simply wouldn't have been possible to work the peak if those points had to be left set towards the Main until an approaching train for the Suburban (often Cricklewood Cars) had come to a stand at the signal - the time taken to stop, set the road & start again would've resulted in delays to the next fast coming up the Main. I've just checked my copy of the (1972) Block Regs (BR29960, the standard version that was't appliccable to the WR). The preamble to the AB Regs includes "Working of Fixed Signals at Diverging Points" and the 4th paragraph reads: "When a signalman at a junction or other diverging point is not in a position to set up the route required for a train until the train is closely approaching the stop signals at such diverging point, he must, as far as practicable, before he sets the points and clears the signal for the required route, satisfy himself that, having regard to the position and speed of the train, it is safe for him to do so." And many's the time the DI watched me swing the junction facing points at Junction Road with LC up and nowt was said (and that was a full-fat 440yd overlap with Reg 1(e) working from Upper Holloway) so I reckon it was OK. But then management in those days wanted to keep the railway running, not tie it up in red tape. (Sorry, my prejudices are showing.) Log in to reply |
| Throwing points in Overlap 08/08/2010 at 21:03 #10591 | |
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mfcooper
707 posts |
Just a quick note. In the NR Absolute Block signalling school course, they teach you that you *cannot* swing points in a clearing point with a train approaching the home signal. The train has to be at a stand at the home signal before the points can be moved. This should be in Rule Book module TS3.
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