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RSC incident investigation (Midleton)

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RSC incident investigation (Midleton)

Unread postby Wilkinstown » Fri Feb 19, 2016 1:04 am

The RSC has produced a post incident inspection report following a planned out of normal incident on the Midleton branch. The document says so much about the convoluted operation of the modern railway and (unintentionally perhaps) highlights some apparently strange aspects of the relatively new signalling layout at Midleton. The report can be read at http://www.rsc.ie/publications/rsc-post ... mber-2014/
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Re: RSC incident investigation (Midleton)

Unread postby Wilkinstown » Sun Feb 21, 2016 8:58 am

Section 6.2.3 states that two options were considered for handling the train at Midleton

1) Authorise the incoming train to pass the signal (491) at danger and subsequently proceed into the siding presumably on the authority of 495 shunt signal with 975 points reversed. Why would this procedure be necessary ? Would it not be possible to signal a train into the siding by clearing both 491 and 495 (Shunt). Even if 491 requires 975 normal the overlap beyond 495 will surely time-out, otherwise no train could ever enter the sidings other than under an "out of normal" arrangement. The only way this makes any sense is that if the overlap timer only starts when a train is standing inside both 495 and 493 signals. It also seems to imply that 975 points could have been reversed and 495 shunt signal cleared if the incoming train was authorised to pass 491 at danger. If this is the case, then the train could have pulled beyond 495 and stopped inside 493 signal and hence cleared the track circuits controlling the crossing. Given the presence of marshals at all doors this would have avoided subsequent issues and been effectively risk free. There would have no necessity for any manual operation of points or for the following regular service from Cork to pass any signals at danger.

2) Signal the train normally into the platform and detrain passengers with the tail of the train (well) clear of the crossing but holding the barriers down (due to the arrangement of track circuits in the station). It seems that 975 points could not have been reversed in these circumstances, a strange inflexibility in the signalling design which would seem to be the route cause of the operational issues which arose on this occasion.

Given the signalling layout shown in the report, would the apparent operational constraints be what might normally be expected ?
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Re: RSC incident investigation (Midleton)

Unread postby AndyB » Sun Feb 21, 2016 11:56 pm

Well, no actually, on any of those counts.

The problem is that the train could not clear the level crossing until passengers in the front four carriages had detrained.

It's quite conceivable that 495 might require a train to stand inside 493 to clear. At 178m (approx) the train was well over the practical length.
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Re: RSC incident investigation (Midleton)

Unread postby Wilkinstown » Mon Feb 22, 2016 7:52 am

Andy,

While the train didn't fully fit on the platform, this was entirely manageable by the use of stewards at each door and so was not really an issue as passengers were disembarked through doors which were on the platform.

The issue exercising my mind is the various apparent inflexibilties in the signalling system, notably 491 apparently requiring 975 normal (trap position) and occupation of the track circuit accross the level crossing locking 975 and preventing clearance of 495. Or alternately would it be unusual were is possible to simultaneously clear both 491 and 495 thus allowing the rear of the train to clear the crossing and avoid disrupting traffic in the town, passing signals at danger and hand winding points to a greater or lesser degree.
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Re: RSC incident investigation (Midleton)

Unread postby Mike Hodgson » Mon Feb 22, 2016 11:42 am

Why did all this take 25 minutes? It sounds as though manual operation of the points did not begin until the train was empty. Is there some reason why the trap points cannot be operated pretty much as soon as the train is stationary in the platform, whilst the passengers are being herded off the train. Does it really take that long to detrain via the available doors ?
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Re: RSC incident investigation (Midleton)

Unread postby AndyB » Tue Feb 23, 2016 8:34 am

That's the thing, though. It is highly undesirable to force passengers to walk to another carriage to disembark (especially if it is a private charter rather than a public railtour), and would probably have created more problems on the train than bringing the first four carriages into the platform, and then the back three, so one way or another you will still have the crossing being blocked.

I don't think you'll ever get 495 to do anything other than approach release, ie the train already in the platform. There is also logic in 491 requiring 975 normal, in order to protect anything in the siding in the case of overrun.

Mike, that's an interesting question. It may be that interlocking was preventing the crossing being released until the train was fully inside signal 493, or in other words, already partly in the siding.
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Re: RSC incident investigation (Midleton)

Unread postby AndyB » Tue Feb 23, 2016 5:59 pm

Also worth noting: the local train arrived in the Down platform while the RPSI train was in Platform 1. Presumably that was part of the reason for the extended closure, potentially also if the crossing was kept closed until the light engine had arrived.

Sequence appears to be:
14:30 Special arrives at Midleton and passengers are detrained (apparently decently quickly)
14:38 Regular railcar due to arrive while special clear of level crossing but not yet inside signal 493 (so the barriers were locked in the down position)
14:43 Light engine due to arrive (actually arrived after train went into the siding)
14:45 Regular railcar due to leave (which cannot have happened until the Light Engine cleared the single line section)

The report is silent as to the consequences on the regular railcar, but for the level crossing to be closed for 25 minutes suggests that it must have departed late.
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Re: RSC incident investigation (Midleton)

Unread postby scarpa » Tue Feb 23, 2016 11:20 pm

The signalling plan revealed an interesting fact .Signal 491 on the plan is a 2 aspect red/green.So under normal working 491 [B] route a driver receives a green aspect up to a fixed red 495 signal.I appreciate the country has its own signalling principles like any other country in the world.
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Re: RSC incident investigation (Midleton)

Unread postby Wilkinstown » Tue Feb 23, 2016 11:35 pm

Andy,

I don't get the point about passengers walking from one carriage to another especially if this could be done at leisure, i.e with the train standing clear of the track circuits controlling the level crossing and unimpaired conditions available for operating into and out of the 2nd platform.

As regards the following regular train the occupation of the line on the Cork side of 493 appears to have locked 974 and required this to be reversed manually and the protecting signal passed at danger, both arriving and departing.

As for 495 it appears that this could not be cleared once 491 was cleared or if 495 was cleared, 491 could not be cleared. The implication in the report is that once 491 been cleared and passed, 495 could not then be cleared until the arriving train was inside 493.

975 points is not protection against an over-run as the points face the yard and not the platform.

It appears that the RSC may has mis-reported the length of time the barriers were held by the special train, other accounts based on timestamps indicate the special train was cleared into the siding 19 minutes after arriving.

The main question in my view is whether the obvious inflexibilities in the signalling system are what might be expected in such a layout ?
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Re: RSC incident investigation (Midleton)

Unread postby Wilkinstown » Wed Feb 24, 2016 12:38 am

Scarpa, 491 at Midleton is red/yellow not red/green despite the diagram reproduced in the report ! I am only aware of one instance in recent years of a colour light green aspect reading directly to a stop signal - at Clonmel where the outer home was a two aspect red/green leading to a semaphore stop signal.This anomaly was corrected some years ago and the colour light amended to display yellow/red aspects only.

There were several locations in Northern Ireland where colour lights were installed to mimic semaphore operation - i.e. the first of a group of stop signals would be preceded by a green/yellow distant placed at braking distance from the first stop signal to which it applied. A green aspect would only be displayed on the distant if all the signals to which it applied were also displaying green as per semaphore practice - the stop signals would only clear to an unrestricted green if all subsequent stop signals in the group were also clear. If a signal was displaying a red aspect the preceding signal would clear from red to green on approach. Such installations existed at Portadown, Belfast Central and on the Lisburn/Antrim line and were installed between 1970 and 1978, but all have either been modified, replaced or de-commissioned.
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Re: RSC incident investigation (Midleton)

Unread postby AndyB » Wed Feb 24, 2016 7:35 am

Wilkinstown wrote:I don't get the point about passengers walking from one carriage to another especially if this could be done at leisure, i.e with the train standing clear of the track circuits controlling the level crossing and unimpaired conditions available for operating into and out of the 2nd platform.

There never was the leisure available. It would have taken far longer to detrain a 7-coach train through four carriages, time which did not exist in the path available.

But that wasn't the point. Making passengers detrain through other coaches gives a bad impression, especially since the queues would be very long for the passengers standing in the front two carriages waiting to detrain via the third carriage. Long queues make unhappy passengers.

The diagram gives the impression that the traps work both directions, so don't mind me on that one. It would still be pretty reasonable in the great scheme of things for 495 only to be capable of being cleared once a train was stopped or nearly so at it, given the proximity of the buffer stops, and I don't understand why you object so much to this.

Re the 19 minutes/25 minutes dispute, the remaining 6 minutes are probably for the light engine to clear the crossing and the local train to depart as I've suggested - with the two movements happening so quickly after the level crossing track circuits were cleared, the minimum clear period before the level crossing could be operated again, and the time it takes to lower the barriers, it may have been considered better to keep the barriers down.
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Re: RSC incident investigation (Midleton)

Unread postby Wilkinstown » Wed Feb 24, 2016 2:08 pm

Andy,

As I understand it the train was disembarked through the carriages which were at the platform when the train initially stopped. I am not aware that the train was repositioned on the platform to facilitate disembaration of the carriages which were not on the platform after the train initially arrived.

While I can understand that the traps at the east end of the station would have to be open to signal a train past 491 and hence 495 would thus have to be at danger. Nonetheless it does seem odd that 975 could not have been reversed and 495 cleared once the train had passed 491 or failing that had been standing on the track circuit in rear of 495 for a short priod.
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Re: RSC incident investigation (Midleton)

Unread postby AndyB » Wed Feb 24, 2016 4:59 pm

Ok, got you now - it's just the way I read the report.

Now we're on the same page - no I don't see why the engine couldn't have entered the siding, even hand-signalled, and the GSV sat just off the platform end. To let the carriage behind the GSV off the platform (ie on 495's overlap) might have got the remaining six carriages clear of 493, or at least far enough forward to permit local operation of the level crossing.
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