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| Unsafe reversing 12/04/2013 at 15:06 #43349 | |
sorabain
72 posts |
Hi, A bit of a random question here about something I started wondering about. In "the real thing" is there any kind of alert or protection against a train that starts going backwards when not authorized to? e.g. is there anything that would pick up track circuits lighting up "backwards" and alert the signaller; and would any of the train protection systems (e.g. TPWS) kick in if a train went the wrong way over them without the driver having enabled the train stop override? I expect a line signalled for bi-directional working would pick this up for sure (at least when you tried to overrun a signal the wrong way), but wasn't sure what would happen in one signalled only for single-direction working. I got to thinking about this as I was wondering what kind of grief malicious players might try to cause in a multi-player driving simulation. Regards, Sorabain Log in to reply |
| Unsafe reversing 12/04/2013 at 15:07 #43350 | |
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jwsetford
164 posts |
TPWS should kick in
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| Unsafe reversing 12/04/2013 at 15:08 #43351 | |
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Rickurd
128 posts |
I would have thought TPWS would kick in. I know AWS inductors only work in 1 direction but I think TPWS will work regardless of the direction
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| Unsafe reversing 12/04/2013 at 15:18 #43354 | |
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Late Turn
699 posts |
AWS magnets are effective in either direction, though will sound a bell in the 'right' direction only (and can be suppressed in the opposite direction). TPWS only works in one direction, so a train running away backwards wouldn't be stopped unless TPWS was provided for a signal in the 'wrong' direction (which should work?) Tom Last edited: 12/04/2013 at 15:19 by Late Turn Log in to reply |
| Unsafe reversing 12/04/2013 at 15:28 #43356 | |
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John
884 posts |
It's not quite the same scenario that you describe, but in RSSB's RED 34 reconstruction, a signaller mistakenly authorised a driver to make a wrong direction movement into a section which was already occupied by a train moving in the right direction, resulting in a near head on collision. In the IECC an alarm went off, but I'm not sure if this was because the train ran through a set of points. Last edited: 12/04/2013 at 15:32 by John Log in to reply The following user said thank you: sorabain |
| Unsafe reversing 12/04/2013 at 15:35 #43357 | |
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Danny252
1461 posts |
" said:AWS magnets are effective in either direction, though will sound a bell in the 'right' direction only (and can be suppressed in the opposite direction). TPWS only works in one direction, so a train running away backwards wouldn't be stopped unless TPWS was provided for a signal in the 'wrong' direction (which should work?)Quite surprised that TPWS works in the way it does (i.e. it's possible, even normal, to pass over an energised trigger loop without it being an issue) - it seems that if the arming loop isn't energised due to a failure, the trigger loop won't have any effect at all? Last edited: 12/04/2013 at 15:36 by Danny252 Log in to reply |
| Unsafe reversing 12/04/2013 at 15:37 #43358 | |
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Late Turn
699 posts |
That's my understanding Danny - that should be indicated as a failure though, so trains can be cautioned if necessary. Tom Log in to reply |
| Unsafe reversing 12/04/2013 at 15:50 #43360 | |
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dwelham313
139 posts |
It's very difficult nowadays for a runaway to occur, you'd struggle to release the brakes on most traction without a master key in, in which case AWS would stop the train as it rolled past the first signal as Late Turn describes. Without a master key in AWS/TPWS wouldnt work. I seem to recall a 66 ended up 'on the deck' a few years ago after running away and being routed into a sand drag as the only means to stop the runaway! To give a bit more info on TPWS, it only works in the signalled direction of travel and is comprised of two 'loops', the arming loop and the trigger loop. The arming loop detects the trains position (in the case of a signal it's positioned right alongside the signal, and is only 'armed' when the signal is a danger) and the trigger loop (located immediatly next to the arming loop) will trigger the TPWS and stop the train. A train travelling in the wrong direction will pass over the trigger loop first, but the trains TPWS system is not armed (it hasnt yet passed over the 'arming' loop)and therefore TPWS will not activate. Last edited: 12/04/2013 at 16:03 by dwelham313 Log in to reply The following users said thank you: GeoffM, sorabain |
| Unsafe reversing 12/04/2013 at 15:59 #43361 | |
GeoffM
6376 posts |
I'm not sure AWS would cause a train to stop in the wrong direction in an auto section. If we assume 200yd overlaps and 200yds from the AWS ramp to the signal, a train would have to be over 400yds long otherwise the auto signal would change to a proceed aspect once the train cleared the track beyond the signal. In IECC there would be an alarm, "track circuit occupied unexpectedly". Also on Westcad and MCS if they have track circuit monitoring enabled on the specific workstations. SimSig Boss Log in to reply The following users said thank you: John, sorabain |
| Unsafe reversing 12/04/2013 at 16:32 #43367 | |
Peter Bennet
5402 posts |
" said:
Sounds like the meeting where we had Euston chained to Wembley Sub - all sorts of shenanigans went on that day with trains re-appearing "wrong line" on Euston and the like. Peter I identify as half man half biscuit - crumbs! Log in to reply |
| Unsafe reversing 12/04/2013 at 16:35 #43370 | |
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Firefly
521 posts |
AWS would work if the master key is in as dwelham313 describes AWS works by Arming the system with a North Pole up permanent magnet and then if the signal is at green a South Pole up electro magnet makes the Bell ring and Sunflower go black. If a train is travelling in the wrong direction it will go over the South Pole electro first (ignoring it) and then it will see the North Pole permanent magnet. There will be no South Pole electro after the permanent so the brakes will apply in just the same way they would if the train was approaching a cautionary aspect or speed restriction. FF Log in to reply The following user said thank you: sorabain |
| Unsafe reversing 12/04/2013 at 16:40 #43373 | |
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Late Turn
699 posts |
" said:I'm not sure AWS would cause a train to stop in the wrong direction in an auto section. If we assume 200yd overlaps and 200yds from the AWS ramp to the signal, a train would have to be over 400yds long otherwise the auto signal would change to a proceed aspect once the train cleared the track beyond the signal. I'd not thought of that one! If it was rolling backwards, with no key in at the previously trailing end of the movement, the AWS wouldn't catch it until the previously leading end of it passed over the magnet (surely?), by which time the associated auto signal would definitely have cleared! Log in to reply |
| Unsafe reversing 12/04/2013 at 16:48 #43375 | |
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Firefly
521 posts |
Quote:Quite surprised that TPWS works in the way it does (i.e. it's possible, even normal, to pass over an energised trigger loop without it being an issue) - it seems that if the arming loop isn't energised due to a failure, the trigger loop won't have any effect at all? TPWS works as Late Turn describes. The system detects if the loops are energised and when both loops are energised you get a system healthy output (Energises a relay called the VCR). The signal in rear of the TPWS protected signal checks to see if either TPWS loops are healthy OR if the signal concerned is showing a proceed aspect. If either of these conditions are TRUE the signal in rear will clear to a proceed aspect allowing a train to approach a TPWS protected signal. If the TPWS signal is at Danger and there is no TPWS healthy output then the signal in rear will not be able to clear to a proceed aspect, therefore a train will not be able to approach the protected signal with a failed TPWS loop. (unless cautioned by the signaller) The only very small risk is that if the signaller replaces the TPWS protected signal to danger after the approaching train has passed the signal in rear then there is nothing in the signalling system to protect the failure, however the TPWS protected signals indication will show failed on the panel (no red indication just like a lamp failure) and most signallers would then get straight on the CSR/GRM-R if fitted. Log in to reply |
| Unsafe reversing 12/04/2013 at 17:27 #43383 | |
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Ron_J
331 posts |
As has been stated, in areas controlled by IECC/MCS/WestCAD unexpected occupation of track circuits will alarm directly to the signaller. ERTMS levels 2 and 3 both feature software (called D_NVROLL) on the trains themselves which detects wrong direction movement and run aways (unexpected movement of over 4m in distance for each) and will apply emergency braking automatically. The issue of run away wrong direction movements was dealt with in this RAIB report. Last edited: 12/04/2013 at 17:29 by Ron_J Log in to reply |
| Unsafe reversing 12/04/2013 at 17:43 #43385 | |
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Danny252
1461 posts |
" said:The signal in rear of the TPWS protected signal checks to see if either TPWS loops are healthy OR if the signal concerned is showing a proceed aspect. If either of these conditions are TRUE the signal in rear will clear to a proceed aspect allowing a train to approach a TPWS protected signal. If the TPWS signal is at Danger and there is no TPWS healthy output then the signal in rear will not be able to clear to a proceed aspect, therefore a train will not be able to approach the protected signal with a failed TPWS loop. (unless cautioned by the signaller)Ah, that's somewhat better! Log in to reply |
| Unsafe reversing 12/04/2013 at 17:46 #43386 | |
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Late Turn
699 posts |
Just out of interest Firefly, is TPWS at the home signal generally included in the block controls? I've never had cause to discover whether our's is or not!
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| Unsafe reversing 12/04/2013 at 17:55 #43387 | |
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Ron_J
331 posts |
I've certainly worked a box where it was, and I'm sure I've also worked boxes where it isn't. We're talking mechanical boxes/absolute block here.
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| Unsafe reversing 12/04/2013 at 18:24 #43389 | |
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Late Turn
699 posts |
Ta Ron - I certainly didn't expect consistency!
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| Unsafe reversing 12/04/2013 at 20:00 #43395 | |
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Firefly
521 posts |
Quote:Just out of interest Firefly, is TPWS at the home signal generally included in the block controls? I've never had cause to discover whether our's is or not!In absolute or tokenless block areas we usually monitor the health of TPWS loops using an FIU (Failure Indication Unit). These sit on the block shelf and set off a buzzer and a bright blue light if a loop should fail meaning that a signaller can then take the appropriate action to protect the failure. If we used the standard method of combining the health monitoring with the signal lamp proving circuit failure of the home signal TPWS would prevent you giving a line clear to the box in rear and I think that probably means that pilotman working needs to be implement and certainly introduces a greater risk of human error. Log in to reply |
| Unsafe reversing 12/04/2013 at 20:23 #43400 | |
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Late Turn
699 posts |
Yep, we have an FIU on the block shelf for our one TPWS-fitted signal (Down Home on the main) - I wasn't sure whether it was also tied into the block, but what you say makes sense. The block controls do prove the home (and distant) normal though, and in one direction only (bizarrely) also prove that the signal lamp's lit - either of these becoming defective does stop a LC being given, but that thankfully involves little more than talking the driver past the section signal in rear at Danger (and advising him of the circumstances if necessary, of course). Tom Log in to reply |
| Unsafe reversing 12/04/2013 at 21:54 #43402 | |
Steamer
3984 posts |
Is this a case in which 2-8 (home signal defective) would be sent?
"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 |
| Unsafe reversing 12/04/2013 at 22:40 #43403 | |
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Firefly
521 posts |
Suspect most signallers would just pick up the phone! If you send 2-8 it could result in the other signaller having to scramble for the rule book to work out what it meant. :dry: Even if they were au fait with all of the infrequently used bell codes they will end up talking to each other on the phone about the problem anyway, so there's little point in doing it with the bells. Last edited: 12/04/2013 at 22:41 by Firefly Log in to reply |
| Unsafe reversing 13/04/2013 at 05:10 #43407 | |
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Late Turn
699 posts |
Give us a little bit of credit for our Rule Book knowledge...  You're right though (in theory as well as in practice) - the necessary arrangements should be made by telephone if possible, with 2-8 or 8-2 only being used (to acknowledge 'is line clear' if telephone communication isn't available. Generally, though - in the age of voice recorders - if the regs do require a particular bell signal to be sent, then it'll be sent even if both Signalmen are on the phone to each other at the time!Tom Log in to reply |
| Unsafe reversing 13/04/2013 at 10:31 #43408 | |
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Firefly
521 posts |
Quote:Give us a little bit of credit for our Rule Book knowledge...Ooops, my bad :blush: I can remember it all kicking off down my way when one signalman sent "Blocking Back inside Home signal" to the next box and the phone was quickly picked up to ask WTF was that! In fairness to the signaller that didn't know the code it was track circuit block regs between the 2 boxes with trains described by block bell so not sure if it really applied or not. Quote: Generally, though - in the age of voice recorders - if the regs do require a particular bell signal to be sent, then it'll be sent even if both Signalmen are on the phone to each other at the time!I'll have to suggest to management that it would be worth monitoring the block bell tapper/plunger in a form of black box recorder to ensure that regs are strictly adhered when signallers are both on and off the phone! :evil: Log in to reply |
| Unsafe reversing 13/04/2013 at 10:41 #43409 | |
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Late Turn
699 posts |
I think I'd be equally puzzled if someone tried to block back on a TCB line . As for recording block bells - is it done anywhere? Not sure if I'd heard somewhere that it was. We're all well behaved though, of course :silly: .
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