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PoSA 06/07/2015 at 16:12 #73958 | |
GeoffM
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RE interlockings, yes the US definition and the UK (+Europe+....) definition is very different. If you think of a simple single line with a passing loop ("siding" in US parlance), the Americans would stick two interlockings on that: one for each end of the loop. Each interlocking in this case would have a single point ("switch"![]() Interlockings in the UK (+Europe+...) don't have any relevance or meaning to drivers of trains - or even signallers generally. The above example would bundle probably a couple of those passing loops into a single interlocking, with the autos between as well. The interlocking covers as much as it can, leaving a little spare capacity in the case of SSI/Westlock/Smartlock where they're limited to 63 trackside modules. SimSig Boss Log in to reply |
PoSA 06/07/2015 at 16:33 #73960 | |
Steamer
![]() 3958 posts |
" said:You'd think that, but all new (and some older) light rail systems are being outfitted with ATC outside of street operation.The opposite is happening over here- Manchester's tram system (Metrolink) used to have fixed blocks on the segregated sections, but has now changed to line-of-sight on both street and segregated. 'Signals' are only provided at junctions and road crossings, where they're interlocked with the traffic lights. Quote: Regarding Call-on signals (or PoSA signals as someone saw fit to rename them)I think there's still a technical difference: I'm fairly sure PoSA consists of two white lights flashing, whereas standard call-ons are solid white. " said: The interlocking covers as much as it can, leaving a little spare capacity in the case of SSI/Westlock/Smartlock where they're limited to 63 trackside modules.Out of interest, how much can a 'trackside module' consist of? What I mean is, does it include an entire signal (including route indicators etc.) or only parts? Would it be one per point end, or one per group of ends which always swing together, crossovers being the obvious example? "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 |
PoSA 06/07/2015 at 16:39 #73961 | |
headshot119
![]() 4869 posts |
" said:RE interlockings, yes the US definition and the UK (+Europe+....) definition is very different. If you think of a simple single line with a passing loop ("siding" in US parlance), the Americans would stick two interlockings on that: one for each end of the loop. Each interlocking in this case would have a single point ("switch"That makes a lot more sense now you've explained it. "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 |
PoSA 06/07/2015 at 16:48 #73963 | |
GeoffM
![]() 6344 posts ![]() |
" said:" said:Not just aspect but the rules and logic are quite different too.Regarding Call-on signals (or PoSA signals as someone saw fit to rename them)I think there's still a technical difference: I'm fairly sure PoSA consists of two white lights flashing, whereas standard call-ons are solid white. " said: " said:Broadly speaking, each module can handle one 4-aspect signal, two 3-aspect signals, or 2 points. I think the points modules can drive multiple ends but for detection purposes are normally split these days. Each module (whether point or signal) has 8 usable outputs and 8 usable inputs. What is not used for the signals/points can be used for other things, such as track section inputs (TCs/axle counters), feathers, theatre boxes, TRTS plungers, etc.The interlocking covers as much as it can, leaving a little spare capacity in the case of SSI/Westlock/Smartlock where they're limited to 63 trackside modules.Out of interest, how much can a 'trackside module' consist of? What I mean is, does it include an entire signal (including route indicators etc.) or only parts? Would it be one per point end, or one per group of ends which always swing together, crossovers being the obvious example? SimSig Boss Last edited: 06/07/2015 at 16:53 by GeoffM Log in to reply The following user said thank you: Steamer |
PoSA 07/07/2015 at 14:20 #73986 | |
Mattyq
![]() 259 posts |
Jersey_Mike, suggest you read the excellent book "Railway Operations and Control" by Joern Pachl. He gives a worldwide précis of rail operations and how they compare/differ to each other. Suffice it to say that North American practices are essentially different to the rest of the world in many aspects. On several occasions, the text reads "(such and such) is achieved by (such and such) except in North America". http://www.joernpachl.de/roc.htm Not fat ..... fluffy!! (G Iglesias) Log in to reply |
PoSA 07/07/2015 at 15:16 #73987 | |
Jersey_Mike
![]() 250 posts |
" said:I think there's still a technical difference: I'm fairly sure PoSA consists of two white lights flashing, whereas standard call-ons are solid white.Whoops, thanks for calling that to my attention. Can someone explain the rules difference between the two? Reminds me of the differences here between Restricting, Stop and Proceed and Restricted Proceed. " said: RE interlockings, yes the US definition and the UK (+Europe+....) definition is very different. If you think of a simple single line with a passing loop ("siding" in US parlance), the Americans would stick two interlockings on that: one for each end of the loop.There are occasional exceptions where short passing loops are within one single logical interlocking (or surrounded by one). See the outline of FAR HILLS interlocking here. " said: Each interlocking in this case would have a single point ("switch"It might be a distinction without a difference, but over here automatic signals (and even some controlled signals) are not considered interlocked. I'm sure it is defined somewhere in regulations, but signals that respond to block state without notions of conflicts or routes appear to be subject to reduced levels of scrutiny. One will frequently see lines where automatic signals are replaced, but interlockings are left as is because of testing and certification requirements for interlockings. Texas once regulated every interlocking in the state (even numbering them sequentially), which would not have been practical if an interlocking was not seen as a compact, discrete thing. This also applies to automatic systems of single track operation like Absolute Permissive Block that uses spring switches and automatic signals with absolute indications. Those are often not considered interlockings with station, block limit or controlled point being the operative term. " said: The relevance for train crews isn't huge, but it is still important. The most significant is that within interlocking limits a train cannot reverse direction without permission. (Outside of interlocking limits trains are usually free to reverse within their own block.) Some railroads give interlockings their own class of movement authority, others (typically western railroads) do not, just adding the special interlocking rules as addenda to the other movement authorities. Under NORAC and CSX, which both use interlocking rules as a movement authority, interlocking rules can extend between adjacent interlockings. Usually this means there is relaxed traffic control so two conflicting movements can be admitted into opposite ends of the same track (at restricted speed of course). Also movements that might normally need a track warrant to be admitted to a main track segment would not need one to occupy a section of track operating under interlocking rules. If things weren't complicated enough, while all interlockings are controlled points (CP), not all controlled points are interlockings. A CP is simply a signal controlled by an signaler. An interlocking has a notion of length, a pure CP is just a point, a single signal, and some railroads treat them differently. For example trains can reverse without permission if they are straddling a CP just like an automatic signal. Log in to reply |
PoSA 07/07/2015 at 15:32 #73988 | |
GeoffM
![]() 6344 posts ![]() |
I was trying to keep it simple, Mike! There are always exceptions, especially where age of installation differs. There was the case of that Amtrak engineer getting confused between two aspects that were visually identical but meant very different things - on one journey, on two different railroads a few miles apart. Something NORAC and GCOR might have prevented but I guess nobody wanted to change "their" system to a standard one.
SimSig Boss Log in to reply |
PoSA 07/07/2015 at 15:42 #73989 | |
clive
![]() 2766 posts |
" said:A signal module has 8 outputs which can go to signal lamps, feathers, RA indicator, AWS magnet, TPWS module, etc; one output can go to more than one place. Some, but not all, outputs can be configured to permit flashing. It then has 2 current detection inputs (used for lamp proving) and 6 generic inputs. So in the simplest case it can drive two 3-aspect signals each with an ARS magnet and in addition get reports from 6 track circuit relays, plungers, or whatever. Devices not needing a controlled output (like track circuits) don't consume any of the 8 inputs (there are other outputs such as the "red retaining feed" and power for TCs). Bigger signals will need more contacts so that they have a signal module of their own instead of sharing one. A points module has 4 pairs of N/R drives for four separate point ends, but it can only work two separate numbered points; each of the four pairs is assigned to one or the other. It has 4 points detection inputs (N and R for each of the two) and 4 generic inputs. Log in to reply |
PoSA 07/07/2015 at 16:02 #73990 | |
Steamer
![]() 3958 posts |
" said:" said:PoSA rules are available here. I can't seem to find the section of the rule book that formally defines the normal signal aspects though.I think there's still a technical difference: I'm fairly sure PoSA consists of two white lights flashing, whereas standard call-ons are solid white.Whoops, thanks for calling that to my attention. Can someone explain the rules difference between the two? Reminds me of the differences here between Restricting, Stop and Proceed and Restricted Proceed. "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 |
PoSA 07/07/2015 at 16:28 #73993 | |
Jersey_Mike
![]() 250 posts |
" said:I was trying to keep it simple, Mike! There are always exceptions, especially where age of installation differs. There was the case of that Amtrak engineer getting confused between two aspects that were visually identical but meant very different things - on one journey, on two different railroads a few miles apart. Something NORAC and GCOR might have prevented but I guess nobody wanted to change "their" system to a standard one.Engineers, especially Amtrak engineers, need to be familiar with the operating rules they are working under. In many cases the operating rules catered to ways that the railroads and signaling systems were constructed. Anyway, the confusion only resulted in a bit of a rear ender with a goods train resulting in no serious injuries. " said: PoSA rules are available here. I can't seem to find the section of the rule book that formally defines the normal signal aspects though.Yeah, I read those rules and I wasn't sure how they could be markedly different from the steady on \ indication. Log in to reply |
PoSA 07/07/2015 at 16:31 #73994 | |
mfcooper
![]() 707 posts |
" said:" said:Essentially, the normal 2-white-diagonal-light steady aspect can refer to a number of things:" said:PoSA rules are available here. I can't seem to find the section of the rule book that formally defines the normal signal aspects though.I think there's still a technical difference: I'm fairly sure PoSA consists of two white lights flashing, whereas standard call-ons are solid white.Whoops, thanks for calling that to my attention. Can someone explain the rules difference between the two? Reminds me of the differences here between Restricting, Stop and Proceed and Restricted Proceed.
and others I have forgotten A POSA aspect (as above, but flashing) is essentially only used to keep trains moving through failures and disconnections. NB: In addition to Steamer's link to the POSA Rule Book Module, here is a link to the Handbook explaining UK signal aspects and line-side signs. Last edited: 07/07/2015 at 16:37 by mfcooper Log in to reply |
PoSA 07/07/2015 at 16:47 #73996 | |
Mattyq
![]() 259 posts |
" said:" said:By "Engineers", are you using American vernacular as in "Train Driver" or the global term "Engineers" as in the overpaid ( :evil: ) professionals who design, install, commission and (to a lesser degree) maintain the signalling equipment?I was trying to keep it simple, Mike! There are always exceptions, especially where age of installation differs. There was the case of that Amtrak engineer getting confused between two aspects that were visually identical but meant very different things - on one journey, on two different railroads a few miles apart. Something NORAC and GCOR might have prevented but I guess nobody wanted to change "their" system to a standard one.Engineers, especially Amtrak engineers, need to be familiar with the operating rules they are working under. " said: In many cases the operating rules catered to ways that the railroads and signaling systems were constructed. Anyway, the confusion only resulted in a bit of a rear ender with a goods train resulting in no serious injuries.The short and VERY generalised answer: PoSA (flashing white) is for working a train through a failed block section, shunt aspect (steady white) is for shunting (what you call "switching"). Trains may not enter an occupied section on a PoSA aspect. Trains most certainly ARE allowed to enter an occupied section on a shunt aspect. Now, I'm answering this from the other side of the globe and stand to be corrected by my UK counterparts! But that's how it reads to me (plus a little operational knowledge). Not fat ..... fluffy!! (G Iglesias) Log in to reply |
PoSA 07/07/2015 at 17:53 #73999 | |
Jersey_Mike
![]() 250 posts |
" said:Locomotive Engineers. Don't call them Drivers as they are likely to take offense. " said: Why is there a distinction there? A hazardous situation is a hazardous situation and trains should be operated in the same manner in both situations. Here are the rules governing the same situation from the GCOR rulebook. Quote: 9.2.13 RESTRICTINGQuote: 6.27 Movement at Restricted SpeedThe only distinction is that in some situations you have to stop first before resuming. Log in to reply |
PoSA 07/07/2015 at 18:10 #74000 | |
mfcooper
![]() 707 posts |
" said:
What definition of "hazardous situation" are you using? Plenty of day-to-day railway tasks can be hazardous unless all the safety procedures are followed. Entering an occupied section in day-to-day operation normally only happens when freight or empty passenger trains are sharing a line in a siding or yard, or passenger trains are sharing a line within designated platforms (not all stations allow this - The majority do not). These "normal" movements are controlled with standard subsidiary signals (constantly lit 2-diagonal-white-lights), all as part of the controlling signalling system. POSA are only used for failures and disconnections. They *might* be used (can anyone confirm?) to allow an assisting train to access a failed train, but this would be in a location where two-in-a-section ("Permissive Working" ![]() Remember, POSAs are still new the the UK railway. Before them, in any of failures I have mentioned in this and my previous posts, a signaller would have to manually set all the points and then authorise the train to pass the signal at danger. For this movement there is no route locking from the signalling system, and mistakes are *possible*. In areas with POSAs, these movements use the safety of the signalling system (interlocking) to set the route correctly and in a much more safe manner. Log in to reply |
PoSA 07/07/2015 at 18:26 #74001 | |
mfcooper
![]() 707 posts |
Further examples (Using London Victoria, which currently does *not* have POSA aspects) 1) Track circuit failure, London Victoria, within the station throat. In this case, the failed occupied track circuit will hold any signalled routes over this track circuit at danger. Before POSA: Before allowing a train to move over this portion of track, the signaller has set all their points in the required position and talk the train past the signal at danger. If the signaller has put any set of points in the wrong position, then we start having major problems! After POSA: The signaller can set up the POSA route into the platform, using the safety of the interlocking to prove the route is set correctly. As London Victoria allows two (or more) trains to share platform space, in both cases the signaller would have to tell the driver if they were going into an empty or an occupied platform. 2) Track circuit failure, London Victoria, buffer-stops track circuit [platform-signal-end track circuit is clear] Normally, the first train to enter the platform will receive a single yellow aspect on the last ("Home" ![]() If the buffer-stops track circuit has failed and remains occupied in an empty platform, the signalling system just sees the occupied track circuit. The "Calling-On" signal can still be given to an arriving train, but a signaller would tell the driver that there is a failure and that the platform is clear. A POSA signal is not required here, because the signaller is still using the safety of the interlocking to allow the movement to take place. EDIT: If the platform-signal-end track circuit was occupied, then the signalling system would believe the platform is full and wouldn't allow both the signal yellow *or* the calling-on to be displayed. The signaller would then have to do what I explained in example 1. Last edited: 07/07/2015 at 18:33 by mfcooper Reason: more typos than you can shake a stick at! Log in to reply |
PoSA 07/07/2015 at 19:16 #74002 | |
Jersey_Mike
![]() 250 posts |
" said:Entering a potentially obstructed block or a block with a possible broken rail. " said: That your operating is either overly paranoid or uses drivers that cannot be relied upon not to hit other trains aside...why does the driver need to be presented with different signal indications in those two situations? The method of operation, proceeding prepared to stop within vision, is the same. It doesn't matter what the nature of the hazard is. Differentiating POSA and Call-on adds needless complexity. " said: Remember, POSAs are still new the the UK railway. Before them, in any of failures I have mentioned in this and my previous posts, a signaller would have to manually set all the points and then authorise the train to pass the signal at danger. For this movement there is no route locking from the signalling system, and mistakes are *possible*. In areas with POSAs, these movements use the safety of the signalling system (interlocking) to set the route correctly and in a much more safe manner.Could the shut signal not be displayed in such a situation? That's what I thought it was there for! Here's a fun video showing the new signal progression at LEAMAN interlocking. Note how quickly the Stop and Proceed indication displays after the passage of the train. https://www.youtube.com/watch?v=CFmGya4HBhI What is probably even more alarming to you is that on this line all intermediate signals have been removed in favor of cab signals only. When one's cab signal changes to this you slow down and then stop when you see a train in front of you. Anyway I'm only pointing this out since after you've borrowed our signals you might we well use them properly. ![]() Last edited: 07/07/2015 at 19:19 by Jersey_Mike Log in to reply |
PoSA 08/07/2015 at 09:24 #74014 | |
kbarber
![]() 1723 posts |
" said:
I think that neatly sums up the difference in our operating philosophies, don't you? Log in to reply |
PoSA 08/07/2015 at 09:29 #74015 | |
GoochyB
![]() 222 posts |
" said:" said:and I thought it was us that " said: uses drivers that cannot be relied upon not to hit other trains Log in to reply |
PoSA 08/07/2015 at 11:38 #74018 | |
Jersey_Mike
![]() 250 posts |
" said:" said:Our tickets prices are still affordable and our goods network actually manages to get lorries off the road. One accident where one engineer misread one signal is an anecdote, not data. There hasn't been a similar incident since and crash resistant rolling stock, mitigated the accident. Regarding permissive working, if drivers are relied upon to stop at bumper blocks other, non-train obstructions or employ it at station platforms, why not use it generally? Has there been a studying that calculated the number of accidents that might result from using PoSA to allow trains to bunch up? I guess one "good" reason not to that I found while using SimSig is that it often screws up the train description system when I bunch a number of short trains into one block. Is that an accurate part of the simulation because that is a bit of a pain to deal with. BTW, fun story. I was hanging out at the rear of Train 30 out of Chicago once and we were stopped for a bridge opening at CP-509. NS dispatcher had put a Wolverine train in behind us on the same track and a bunch of the people who were wondering what I was looking out (from the rear of the train) thought the other train was going to hit us because I explained it was supported to do that. I thought I had a better picture, but this was all I could find. Log in to reply |
PoSA 08/07/2015 at 16:43 #74029 | |
TimTamToe
![]() 658 posts |
" said:Yes because you shouldn't be bunching lots of small trains into one section! Log in to reply |
PoSA 08/07/2015 at 17:02 #74031 | |
Steamer
![]() 3958 posts |
" said:There hasn't been a similar incident since and crash resistant rolling stock, mitigated the accident.I believe the phrase is "Riding your luck". Quote: Regarding permissive working, if drivers are relied upon to stop at bumper blocks other, non-train obstructions or employ it at station platforms, why not use it generally? Has there been a studying that calculated the number of accidents that might result from using PoSA to allow trains to bunch up?Yes, the train describer is accurate. The only places the train describer is likely to handle more than one train per section correctly is where permissive working is authorised. If you're telling trains to pass signals at danger to bump them along, then (a) you're doing it wrong and (b) the describer won't work properly, due to (a). 'Permissive block' used to exist back in steam and early diesel days, on goods lines only. Any remaining sections are few and far between. I suspect the usual reasons against it apply- long braking distances, and reduced visibility around curves. "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 |
PoSA 08/07/2015 at 18:59 #74035 | |
clive
![]() 2766 posts |
" said:There was also the working arrangements on the New Lines, correctly simulated in SimSig Euston. In the case of a failure this could result in several passenger trains waiting buffer-to-buffer. Log in to reply |
PoSA 09/07/2015 at 00:03 #74045 | |
Hooverman
![]() 306 posts |
" said:I guess one "good" reason not to that I found while using SimSig is that it often screws up the train description system when I bunch a number of short trains into one block. Is that an accurate part of the simulation because that is a bit of a pain to deal with.That would see you relieved of duty rather rapidly with possibilty of being DA'd and most defiantly a friendly tea and biscuits chat with the governor in their office, except that it wouldn't be friendly and there would be no tea and biscuits but a union rep might help. Log in to reply |
PoSA 09/07/2015 at 07:40 #74047 | |
kbarber
![]() 1723 posts |
" said:" said:There was also the working arrangements on the New Lines, correctly simulated in SimSig Euston. In the case of a failure this could result in several passenger trains waiting buffer-to-buffer. I rather think this was an attempt to import US-style working into the UK, courtesy of Arthur Bound, the LMS CS&TE, who was strongly influenced by US practice. The signalling installed on the 4th-rail electrified lines between Barking and Upminster was identical, I believe. And London Transport - again influenced by US practice (courtesy of Yerkes' ownership of the early tube network) have always used stop & proceed working, with only local areas appearing on the diagrams in signal boxes. (Regulating Rooms invariably have a full display more akin to main line practice.) But it hasn't always worked well, with a number of unfortunate incidents marked up against it over the years. Log in to reply |
PoSA 09/07/2015 at 10:45 #74054 | |
clive
![]() 2766 posts |
" said:" said:" said:There was also the working arrangements on the New Lines, correctly simulated in SimSig Euston. In the case of a failure this could result in several passenger trains waiting buffer-to-buffer. Indeed. Quote: No, it wasn't. I know a number of the usual sources say so, and it took me a long time to find out otherwise. In my Copious Free Time I need to write it up. Quote: I believe that, after the third or fourth such rear-end collision in the Leyton-Stratford area, it was finally abolished. Log in to reply |