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| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 13:50 #45813 | |
maxand
1637 posts |
Although approach control has been mentioned in several places in the forum and Wiki, it's not clear to me whether SimSig adopts any particular way of distinguishing them from other running signals. There are some very learned discussions on approach control in the forum, such as this one, but they are generally way over my head as they require expert local knowledge. I'm more interested in examples related to actual sims. I'm excluding approach locking (which applies to most signals) and also signals ahead of operator-controlled crossings, which can mimic approach control. I'm thinking more of approach controlled signals at turnouts. Clive Feather's excellent article on junction signalling illustrates several methods used in real life, but there don't seem to be too many instances of them in SimSig except perhaps Westbury (which I haven't played yet), where the manual states "Many junctions use approach control" - without disclosing actual signal numbers. Carlisle's manual states "Conditional Aspects :- Will cause certain signals to become approach controlled which happens on the real panel." These at least seem to be marked by letter abbreviations. Is discovering them meant to be part of the fun? The Wiki has a section on flashing yellow aspects but I have not seen this in any sims. The only genuine approach-controlled signal I've encountered so far is one at Llangollen, which prompted me to ask for help. It's frustrating when a sim doesn't work as expected. The negative-shoe detector at signal 8 in Wembley Sub I guess could be regarded as a form of approach control, though this is not termed such in Clive's manual and is there not to reduce speed of an approaching train but simply to ensure trains are routed correctly. Quite possibly I've missed a few on the simpler sims or even given up on some not realizing it was approach control which prevented me from setting routes. Are we meant to discover them by trial and error? Perhaps forum members could post some notable examples from earlier sims so that this thread could become a bit of a reference. Thanks. Last edited: 19/06/2013 at 14:02 by maxand Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 13:59 #45814 | |
Peter Bennet
5362 posts |
Approach control does not prevent you setting a route in advance of the train, it just means that the signal will not clear to the expected aspect till the train reaches a certain point in advance of the signal. Some release from red, others from yellow and/or flashing aspects. I know, for example, that Down trains at Woolmer Green (on KX) should get flashing aspects for trains diverging to the DS (I can see them flashing out of the train window as I pass every night). Also I think the DM signal at Hitchin for the Cambridge branch is release from red. I'm sure there will be examples on most Sims somewhere. While I guess it's nice to know I don't think it's essential to play the Sim that you do know where they all are. Peter I identify as half man half biscuit - crumbs! Last edited: 19/06/2013 at 14:00 by Peter Bennet Log in to reply The following user said thank you: maxand |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 14:15 #45815 | |
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John
884 posts |
To answer the question in the title of this topic, with the exception of the conditional aspects on the Carlisle sim, approach-controlled junction signals are not marked in Simsig, nor are they, I suspect, in real life. It's all to do with the speed of the turnout. If the turnout speed is low, say 15/25 mph, then the signal protecting the junction will be held at danger until the interlocking has detected that the trains approach has been slowed sufficiently at which point the signal will clear. For higher speed turnouts, say 40/50 mph(such as the examples Peter mentions), then flashing aspects will be used. These will give the driver advance warning of the route which has been set, but without having to bring the train to a virtual stand. Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 14:20 #45816 | |
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Peter Bennet
5362 posts |
There is an case where it maybe handy to know the "rules" of the signal. That's where the signal has a main and a sub aspect, the sub aspect for trains diverging (say) into a siding and the main aspect has an overlap across the points. If the overlap can't be swung then the route into the siding can't be called till the O/lap has died - proving that the train is (more-or-less) at a stand. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 14:27 #45817 | |
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John
884 posts |
Such as the route into Hitchin Up Yard from the Letchworth direction, or the route onto the goods line at Alexandra Palace. I'm guessing this arrangement is for very low speed turnouts? Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 15:13 #45819 | |
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dwelham313
139 posts |
Entry to Hitchin Up Yard from the Letchworth end is 5mph, and in real life the route can't be set without a member of Hitchin station staff pressing an acceptance plunger in their office. The routing of trains onto the up goods at Alexandra palace is also differnet on the sim - in real life this is an appraoch controlled signal that clears usually before you reach the platform, soemtimes still travelling in excess of 30mph! The points are set at 25mph. But yes the idea behind having to wait for the overlap to die is to prevent the train barreling through at excess speed. Log in to reply The following user said thank you: John |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 15:25 #45820 | |
GeoffM
6287 posts 
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Not being able to swing an overlap into a siding is often because the overlap wouldn't be long enough (200yds for 60mph+ in general). Carlisle sim does have some labels for the conditional aspects but this is not standard. Where it exists in real life is usually just a label stuck on the panel rather than properly etched. Identifying approach controlled signals in itself is worded incorrectly, for it's not the signal that determines the approach control but the route. The same signal can be not approach controlled for the main route, approach controlled from red for the leftmost route, flashing yellows for the next route, and "green if next signal is off, otherwise approach controlled" for the last route. How would you label such a signal? Something I've been working on is a simplified control table generated from the data which the developer can insert into the Wiki. This could include approach control. It already lists all the routes, the from- and to-signal, ARS subareas if applicable, and has a space for notes. SimSig Boss Log in to reply The following user said thank you: John |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 15:53 #45823 | |
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Lardybiker
771 posts |
Approach control applies where this is a difference in speed between the main route and the diverging route and thus the train needs to be slowed down. The severity of the control depends largely on the difference in speeds between the two but there are many other factors involved hence why some step up from yellow, some red and some have flashing aspects. I would guess virtually all sims have some signals in them that are approach controlled. South Humberside I know has a several. The diverging route to Immingham at Brocklesby has a flashing yellow aspect for the diverging route for example. The key is though, as Geoff noted, approach control is on a route by route basis so a signal may have 5 routes from it but only one of those routes may have approach control. The approach locking for different routes from the same signal can also have completely different approach locking arrangements too. That alone makes indicating it difficult. I know on my sims there is no indication there is or is not approach control on a signal. That's where learning an area comes into play as you will see which signals clear straight away and which do not. Last edited: 19/06/2013 at 15:54 by Lardybiker Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 16:04 #45824 | |
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Sacro
1171 posts |
" said:...the signal will not clear to the expected aspect till the train reaches a certain point in advance of the signal.No signal should clear if the train has reached a point in advance of the signal, that would be a SPAD. 
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| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 16:05 #45825 | |
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Hooverman
306 posts |
" said:That's where learning an area comes into play as you will see which signals clear straight away and which do not.Just like real life when you have to spend weeks learning your panel / work station. :-) Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 16:10 #45826 | |
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kbarber
1712 posts |
Further to Geoff's comment, I've never known any way of distinguishing an approach controlled signal in real life - you just set the route and, provided the route calls correctly, let the circuitry do its stuff. If you don't get the route come up white you call the S&T (unless you're still learning the job, of course). If the route calls but the train still stops it's another job for the S&T - perhaps lamp failure or something - and meanwhile you work it as a failure. Where control is from a frame (certainly mechanical, I think I've seen it on a miniature-lever frame(s) too but can't recall the detail) you sometimes get what I know as approach release (not quite sure whether this is official terminology) - it's approach control but rather than working at aspect level in the locking it locks the lever normal until the appropriate track circuit is occupied. That means you have to keep an eye on the approaching train and pull off when the track drops. If you're trying a quick move the trick is to stand holding the lever a fraction away from normal but just clear of the electric lock (maybe having to hold up the catch handle - the catch may not be fully clear of the notch) and wait for the 'clunk' beneath your feet, which is the cue to whip the lever over quick and keep the train on the move... Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 17:45 #45829 | |
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quickthorn
23 posts |
" said:I've seen this written elsewhere, but is it true? In the section dealing with approach control from red, GK/GN0645 "Guidance on Lineside Signals, Indicators and Layout of Signals" contains the paragraph: GN601 The point at which the junction signal displays the OFF aspect for the diverging route does not have to be compatible with the speed reduction required for the diverging route, because the driver should have observed the single yellow aspect and be preparing to stop the train. Reading further into that document, I take it that the junction signal can be released at any time after the train has passed the junction signal distant and any banner repeater signal associated with the junction signal (subject to visibility issues), and is independent of train speed. Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 17:57 #45831 | |
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Danny252
1461 posts |
It often isn't that its timed as being at the diverging speed, but detected as having slowed sufficiently to reach the diverging speed before the junction - much like TPWS will time a train on the approach to a stop aspect to ensure that the driver is braking as expected, but obviously will allow him to approach the signal despite the speed limit past the signal being "0mph", in effect.
Last edited: 19/06/2013 at 17:59 by Danny252 Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 18:05 #45832 | |
Steamer
3925 posts |
I was always under the impression that it was based on track circuit occupancy, and that the signal would clear x seconds after a certain track circuit was occupied, which in effect means that the average speed of the train cannot be above a certain value or the delay period will not have elapsed. If a train fails to slow down for the red signal, it will quite probably trigger the TPWS on the approach to the signal before the signal clears. If you go on a sim with F11, set a route that is released from red, and then occupy the berth circuit, the signal will clear after a certain time delay, the length of which depends on the location. EDIT: Danny posted while I was typing. "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) Last edited: 19/06/2013 at 18:05 by Steamer Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 20:11 #45833 | |
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kbarber
1712 posts |
" said:I was always under the impression that it was based on track circuit occupancy, and that the signal would clear x seconds after a certain track circuit was occupied, which in effect means that the average speed of the train cannot be above a certain value or the delay period will not have elapsed. If a train fails to slow down for the red signal, it will quite probably trigger the TPWS on the approach to the signal before the signal clears. This has the potential to create a SPAD trap, of course, as drivers come to expect it to happen. There was one such (approaching a level crossing not a junction) that drivers exploited to frighten newbie managers on the patch. On the up at Highams Park (next station south of Chingford) the LC was London end of the station, protected by a signal; the signal in rear was approach controlled from red. In reasonable visibility it was possible to see the line clear beyond the platform end from a long way before that rear signal - braking distance plus a bit. The drivers knew that, provided the platform could be seen to be clear, they could approach that signal at 59mph or so and it would clear at the very last second; at 60mph it would be a SPAD. I know that from experience... :sick: and I wasn't the driver! 
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| How are approach-controlled junction signals marked in SimSig? 19/06/2013 at 22:17 #45836 | |
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GeoffM
6287 posts
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" said:I was once on the PATH system in New York, sat at the front where one could have a view of the driver and a part view out the front. There must have been some approach controlled signals or maybe just a train in front, and some sort of protection which would stop the train if it passed a red signal. Which the driver did. Repeatedly. Others you could see the signal clearing less than a second before passing it. Not my kind of driver. 
SimSig Boss Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 20/06/2013 at 03:53 #45838 | |
dmaze
88 posts |
" said:I was once on the PATH system in New York, sat at the front where one could have a view of the driver and a part view out the front. There must have been some approach controlled signals or maybe just a train in front, and some sort of protection which would stop the train if it passed a red signal. Which the driver did. Repeatedly. Others you could see the signal clearing less than a second before passing it. Not my kind of driver. :(I haven't been on PATH, but I know the "normal" MTA subway has both mechanical stops that will put a train into emergency if it passes a red signal, and timer-based signal aspects that enforce speed limits. The MBTA Blue Line subway in Boston also uses timer-controlled signals, and also has the property that drivers will be running at a red signal at full speed (35 mph through the harbor tunnel). A yellow-over-white signal means that the next signal is red, but will clear on a timer (frequently itself to yellow-over-white) if the train observes the speed limit...so just before the train passes a red signal, it blinks, then changes aspect as the train hurtles by. Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 20/06/2013 at 07:20 #45839 | |
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maxand
1637 posts |
Thanks for all your contributions - learnt much from that. Particularly Geoff's comment, echoed by others, that it's the route, not the signal, that determines whether approach control comes into action. The same signal may serve several routes. Maybe that's why a distinguishing symbol for such a signal would make it ambiguous.
Last edited: 20/06/2013 at 07:33 by maxand Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 20/06/2013 at 09:53 #45840 | |
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clive
2738 posts |
" said:Repeater signals on PATH show the same aspect as the signal they are repeating. So he was passing *repeaters* showing red, not stop signals. In the UK, distant signals used to look the same as home signals back in the mid-19th century. It was 1872 before they started to gain fishtail ends; from 1898 some railways added a white > symbol at night (google "Coligny-Welch). Yellow night indications didn't appear until 1916 and yellow arms until 1918. [Dates from www.railsigns.co.uk.] Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 20/06/2013 at 09:59 #45841 | |
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clive
2738 posts |
" said:Although approach control has been mentioned in several places in the forum and Wiki, it's not clear to me whether SimSig adopts any particular way of distinguishing them from other running signals.No, it doesn't. Quote: There's usually too many to list. Simsig supports approach control from red, yellow, and flashing yellow. It's possibly to hack up splitting distants as well. We don't yet support white arrows. Quote: Yes, that's not approach control. From memory, the only approach controlled signals on Wembley Sub are Willesden Junction towards Kensal Green on the up, and the approach into platform 2 on the down. However, it's possible I've forgotten one. Most sims have lots of them. For example, on Cambridge the turnout to the Royston line is approach controlled. There are flashing aspects on King's Cross. Quote: Approach control won't prevent you setting a route. It just holds the signal at a different aspect (e.g. red for approach control from red) until the train gets close. Log in to reply The following user said thank you: maxand |
| How are approach-controlled junction signals marked in SimSig? 20/06/2013 at 15:26 #45847 | |
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GeoffM
6287 posts
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" said:I haven't been on PATH, but I know the "normal" MTA subway has both mechanical stops that will put a train into emergency if it passes a red signal, and timer-based signal aspects that enforce speed limits.That would make sense - approaching an timer control signal slightly too fast, passing it at red, causing a brake activation. " said: Repeater signals on PATH show the same aspect as the signal they are repeating. So he was passing *repeaters* showing red, not stop signals.No, these were stop signals. There is no reason why a train would go into emergency and come to a stand just for passing a repeater. SimSig Boss Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 21/06/2013 at 10:29 #45860 | |
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sorabain
72 posts |
This thread reminded me of this incident (already posted on the RAIB thread) where even an approach controlled signal on a 15 mph diverging route is not fool proof. Reposting again as some might find it interesting in this context http://www.raib.gov.uk/cms_resources.cfm?file=/121121_R242012_Bletchley_Junction.pdf "41 When a train is to take a relatively low speed diverging route at a junction, the signalling system controls the signal protecting the junction so that it displays a restrictive aspect (red or single yellow) until the train is at a specific distance from it1 . The signal will then clear from its restrictive aspect to a less restrictive aspect, dependent on the status of the line ahead, by a process known as approach control. The purpose of approach control is to cause the driver to slow the train down while approaching the junction and to reduce the probability of it exceeding the permitted speed as it takes the diverging route. Signal BY19 at Bletchley Junction is fitted with approach control from a red aspect for diverging moves to the up fast line. 42 Approach control relies upon the driver of a train correctly responding to the signal aspect displayed following the clearance of the junction signal and does not mitigate the risk from a train subsequently being accelerated to an excessive speed before reaching the junction points. This risk is increased in the case of light locomotives and modern rolling stock with rapid rates of acceleration." Last edited: 21/06/2013 at 10:30 by sorabain Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 21/06/2013 at 16:24 #45865 | |
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mfcooper
707 posts |
There are no markings for approach control on the panels at Victoria Area Signalling Centre (my workplace). This is mostly because only a certain route or routes from a signal are approach controlled. I can think of numerous examples at junctions where signals are approach controlled for the diverging route, but not for the "straight" route. There are also some that are only approach controlled if a selection of points are in certain positions[sup](1)[/sup]. All of this information is learnt as a signaller learns their panel/workstation/etc. It would get very confusing to have labels across a panel telling which routes from which signals are approach controlled. [sup](1)[/sup] We have a junction signal, VC789, that can take trains towards Mitcham or Wimbledon. From this signal, only the route to Wimbledon is approach controlled. But, it is only approach controlled if trains are approaching from Streatham on the Down Portsmouth. If they are approaching from Balham, or from Streatham using an unusual shunt route over the Up Portsmouth in the down direction, then the route from VC789 to Wimbledon is NOT approach controlled. Confused yet? Most new starters are 
Last edited: 21/06/2013 at 16:25 by mfcooper Reason: typos Log in to reply The following user said thank you: AndyG |
| How are approach-controlled junction signals marked in SimSig? 21/06/2013 at 16:40 #45866 | |
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John
884 posts |
So, if you're coming off the fast reversible in the down direction, the route onto the Down St Helier is not approach controlled? I suppose that's because the speed limit on the reversible and associated pointwork is the same as the turnout for Tooting? Last edited: 21/06/2013 at 17:00 by John Log in to reply |
| How are approach-controlled junction signals marked in SimSig? 21/06/2013 at 17:46 #45868 | |
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mfcooper
707 posts |
" said:So, if you're coming off the fast reversible in the down direction, the route onto the Down St Helier is not approach controlled? It's also if you are coming off the Down Slow Spur. " said: I suppose that's because the speed limit on the reversible and associated pointwork is the same as the turnout for Tooting? I believe so. The Down Portsmouth (through from Streatham to Mitcham) is a relatively straight piece of railway line, so I assume there is a much higher line speed on this compared to the Down Slow Spur or the Reversible Fast Spur and the lower turnout speed. Last edited: 21/06/2013 at 17:46 by mfcooper Log in to reply |