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| Exclude stationary trains from approach locking? 29/11/2011 at 03:10 #23973 | |
maxand
1637 posts |
In all the sims I've played so far, cancelling a route ahead of a stationary train still causes a 120 second delay. I can't see the logic behind this, and apparently neither can the Railway Group Standard. In their document Approach Locking & Train Operated Route Release, they state: Quote: Approach locking shall be released, after replacement of the signal to danger, by either:Now it could be argued that in real life, a signaller seated miles away in a snug and cosy office might be unable to tell from his display whether a train in the block affected by the signal is still moving or stationary. However, it's also possible that other forms of communication (telephone?) might make him aware of the fact that said train has been stationary for quite a while. That this document makes provision for "a reasonable assurance being obtained" as above implies that in real life, too, there is no need to waste two extra valuable minutes cancelling a route for a stationary train, and ways have been found around it. If this is so, and SimSig players have the extra psychic ability provided by the Train List not just to know whether a train is moving or stationary, but its exact speed at any moment (!), would it not be more practical and realistic to confine the program code dealing with approach locking to moving trains only? 
Last edited: 29/11/2011 at 03:18 by maxand Reason: reworded title of thread Log in to reply |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 07:15 #23977 | |
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ralphjwchadkirk
275 posts |
Refer to Appendix A3. The Standard requires a certain amount of elapsed time depending on type of signal.
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| Re: Exclude stationary trains from approach lockin 29/11/2011 at 08:09 #23978 | |
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Late Turn
699 posts 
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Max, Although you might be able to tell, from looking at the train list in Simsig or looking out of the window of a mechanical box in reality, that a train is at a stand, the interlocking doesn't have that information - and it's the interlocking that enforces the approach locking. The only way the interlocking can prove a train at a stand is for the TC in rear of the signal to be occupied for a specified period. Look at the Moreton-on-Lugg accident over here last year for an unfortunate example of what can happen when you don't provide approach locking! Tom Log in to reply |
| Re: Exclude stationary trains from approach lockin 29/11/2011 at 09:31 #23981 | |
Peter Bennet
5402 posts |
And in certain boxes the approach locking kicks in regardless of where the train is: see Cowlairs on CSCOT, for example, where some signals have a 4 min timeout regardless. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 12:06 #23998 | |
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alvinhochun
249 posts |
This is designed to be fail-safe. You can imagine if the train moves, but the interlocking didn't get the information, the consequences can be serious. Log in to reply |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 12:10 #23999 | |
jc92
3690 posts |
approach locking does apply to stationary trains aswell though. theoretical example. im signaller at station X. i have some ECS waiting to leave so i pull off for it early, forgetting im due a passenger service out on a conflicting path. when replacing the signal, if it has a two minute lock on it, that provides the driver of the ECS 2 mins to pass it at danger, having not realised it was replaced and/or if ive replaced it on him as hes started moving. if he SPADs it during this time it will prevent the passenger train from being signalled protecting both trains. without the approach release, i can have two trains converging.
"We don't stop camborne wednesdays" Log in to reply The following user said thank you: maxand |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 12:18 #24001 | |
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jc92
3690 posts |
" said:the first point is how a signal normally is replaced to danger, ie the passage of a train, no locking required. the third point is used on most sims/boxes where the interlocking will initiate approach locking if a train will receive an ACOA (regardless of whether the driver can see it as the interlocking doesnt know this) theres two ways of obtaining reasonable assurance that a train is stationary 1 by looking out the box window in mechanical areas 2. by having a timeout calculated so that it doesnt release until a reasonable time has passed for the train to pass the signal or stop at it. you will notice overlaps "time out" like this. shunt signals tend to have a 30sec timeout as all movements conducted on them are slow speed over short distances, whereas areas with a 240 sec timeout may control a major junction where a SPAD would be catastrophic. also of note is that in some mechanical installations, home signals will have a 2 min time release regardless of a train approaching or not, as there will be insufficient track circuiting to ascertain this for certain "We don't stop camborne wednesdays" Log in to reply The following user said thank you: maxand |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 12:39 #24003 | |
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maxand
1637 posts |
Thanks jc92 and everyone else for your thoughtful answers to this one. Quote: if he SPADs it during this time it will prevent the passenger train from being signalled protecting both trains. I couldn't quite picture exactly how the ECS driver passing the signal at danger would actually protect the passenger train, but I get your general drift. Would you mind explaining what ACOA stands for? Can't find this anywhere. I guess there's no substitute for safety. Last edited: 29/11/2011 at 12:40 by maxand Log in to reply |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 12:39 #24004 | |
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Late Turn
699 posts
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" said:theres two ways of obtaining reasonable assurance that a train is stationary Remember that the interlocking cannot look out of the window - although the Signalman might have assured himself that the train has come to a stand, the interlocking does not know this - if it is to prevent the route being released in error, it must revert to the second method (i.e. assuming the worst-case, and providing a timed release to ensure that the train has had sufficient time to either stop short of the signal or pass the signal. Quote: also of note is that in some mechanical installations, home signals will have a 2 min time release regardless of a train approaching or not, as there will be insufficient track circuiting to ascertain this for certain Also the case where the additional circuitry to establish whether there is a train approaching cannot be justified - see the Clay Cross area of Trent for an example of this! Log in to reply The following user said thank you: maxand |
| Re: Exclude stationary trains from approach lockin 29/11/2011 at 12:45 #24005 | |
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ipswich
247 posts |
ACOA - Adverse Change Of Aspect: it means when a signaller cancels a route in front of a passing train e.g.: 2R43 for example if hes approaching signal 4 at a green but signalman put signal 5 back to danger signal 4 goes back to a yellow this is adverse change of aspect because the signalman didn't ring driver of 2R43 up but its not adverse if the signalman rang up the driver and asked for permission to put back signal 5 hope this makes sense to you Log in to reply The following user said thank you: maxand |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 12:59 #24009 | |
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maxand
1637 posts |
Perfect sense, thanks a lot ipswich
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| Re: Exclude stationary trains from approach locking? 29/11/2011 at 13:45 #24013 | |
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ralphjwchadkirk
275 posts |
ACOA is not official railway terminology. It was invented by Simsiggers. The signaller also does not need the permission of the driver to put back a signal, he merely needs to make sure the driver is aware the aspect will change to a more Restrictive aspect. Log in to reply |
| Re: Exclude stationary trains from approach lockin 29/11/2011 at 13:47 #24014 | |
headshot119
4869 posts |
" said:ACOA - Adverse Change Of Aspect:Surely the Adverse change of aspect for 2R43 would have been at SY8? "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 The following user said thank you: jc92 |
| Re: Exclude stationary trains from approach locking? 29/11/2011 at 15:35 #24022 | |
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Sam Tugwell
494 posts |
Ah, But 2R43 didnt get ACOA'd did it. He will have been checked down on the approach to Barnt Green (Havent got Saltley open so cannot tell you signal numbers at the mo). He was held at SY8 to be advised of the ongoings at Alvechurch...
"Signalman Exeter" Log in to reply |
| Re: Exclude stationary trains from approach lockin 29/11/2011 at 16:52 #24032 | |
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ipswich
247 posts |
2R43 was first headcode that i thought of at the time as were signal numbers
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