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2012 Q7 Signal Sighting - Hort - 22-09-2013
Hi, thanks for previous comments, I have attempted Q7 of the 2012 paper.
RE: 2012 Q7 Signal Sighting - PJW - 01-10-2013
Sorry haven't got back on this one- life hectic at present.
Basically a pretty reasonable answer
However I think the occurrance of the poor sighting is far more likely to be due to LONGER trains that barely fit in the platform and so have poor visibility from the driver's cab- particularly if the "cab sight lines" are more restricted than previous rolling stock. Tends to be the case nowadays when the cab is designed for better driver comfort in normal operation and indeed safety in the event of a collision- tends to be further back from the windscreen and the front of the train.
I did wonder about the hazards- to me the SPAD is the hazard and which particular accident which might result from it is a matter to reflect on an Event Tree but the hazard would be the same in each case. Not really sure what the examiners wanted here though- being a terminal station it is not one where there will be very many different types of SPAD causes. Perhaps you could have a SPAD because
a) failed to check for signal at all having been given the right away
b) looked across to the parallel signal as own not well visible
c) too close to own signal and therefore read through to the next one ahead.
Feel it needed more than that though......
I thought your answer to part b) was good and apparopriate to the mark allocation.
e) started ok but you didn't really apply it to the two solutions suggested in d) as you had ben asked to do- a bit too much repeat from Yellow Book without actually applying.
Overall though a pretty solid answer that ought to be a decent pass I think.
(22-09-2013, 10:36 PM)Hort Wrote: Hi, thanks for previous comments, I have attempted Q7 of the 2012 paper.
RE: 2012 Q7 Signal Sighting - AdrianM - 25-09-2015
Attempt in exam conditions, took a little over 30mins.
I'd not read the previous attempt nor the input from PJW, so I can see where I should have added more detail.
Any feedback is welcomed. I'm not sure where the 6 marks come from in part c.
Regards,
Adrian
RE: 2012 Q7 Signal Sighting - PJW - 29-09-2015
(25-09-2015, 12:56 PM)AdrianM Wrote: Attempt in exam conditions, took a little over 30mins.
I'd not read the previous attempt nor the input from PJW, so I can see where I should have added more detail.
Any feedback is welcomed. I'm not sure where the 6 marks come from in part c.
Regards,
Adrian
a) Did plenty for the first 4 marks, but it would have been good to have suggested some of the underlying reasons which may have led to problems in the visibility that you have described (you didn't really state much in the way of assumptions)-
- that the footbridge may be obstructing just the route indication above the signal, particularly if the train cab is some distance on the approach to the footbridge which cuts off field of view,
- increased crash resistance of modern rollingstock tends to mean that the driver is positioned further back from the front window and this restricts peripheral visibility (particularly an issue for ground mounted signals- although this not relevant in this case)
- trains may not always be run in full length formations and it is when a short train is at the buffer stop end that platform curvature may be most of an issue,
- right hand mounted signals can be particularly hard for a driver to see from their seat on the left of the train when cab is close to signal and this may be constrained because of the desire that the new trains are as long as possible for maximum capacity.
c) Be careful of wording re what hazards exist;
a derailment or collision counts surely as an ACCIDENT since there is a certainty of loss- there may not be death and perhaps even injury might not result, but there would certainly be property damage and service disruption at the very least and that is a definite loss, not a potential one!
Conversely a signal overrun is a hazard; there may or may not be a train routed over the crossover at that time and so there is a potential for collision and the level of risk associated with a head-on collision is rather more than a rear-end or side-swipe,
similarly there is the potential to run-through the trailing points depending on which lie they happen to be, overspeed is a hazard since derailment is a possible (although in this case probably quite unlikely) outcome,
any overrun will bring an element of service disruption, but the extent of this does depend on the level of traffic at the time and the positions of other trains, so whether significant harm is done does indeed depend on a range of factors and thus is quite uncertain.
d) I agree- think getting these 6 marks would be very difficult- your possibly solutions seem the obvious ones; however don't see that what you wrote was worth more than 4 at most, nor really what else you could have added. I suppose that you could have pointed out that the repeater of no value if the sighting issue was one resulting from front cab close proximity to signal (I may be thinking too much in a mainline context for your answer- a banner repeater would almost certainly go on or on the approach to the footbridge, but if needed the option of a co-acting signal could be provided either ground mounted and/or on the left of the line- I guess that an LU repeater could actually be used in either of these scenarios)
e) This was indeed expecting you to describe the 7 stage process.
Yes could use a Fault Tree to consider the likelihood of the Top Event of SPAD- this would get a combined estimate from the various scenarios which could lead to that occurrence.
Not convinced however that FMEA would be appropriate in such a case; we are really considering the chance of human error here, so we could get some values using the HEART technique re for e.g
- the likelihood of the driver failing to check the signal before departure, perhaps triggered by hearing the points move, closing the doors and then having checked the interlock and checked the CCTV just powering away.
These would be done for the original unmitigated state, then re-done making alterations to reflect your two proposed options and therefore values obtained for the original level of risk and the two others. You should have tied your "options analysis" back to the earlier parts of this question.
The important final thing to make clear is-
1. Risk must not be intolerably high
2. Risk should be reduced to be ALARP and to be able to demonstrate that then the cost of each of the mitigations must be compared to the safety risk reduction it is estimated to have.
3. Whereas a simple cost-benefit analysis is appropriate to non safety risk (is it worth the investment to avoid a possible financial loss?), the assessment of a mitigation of a safety risk is subtly but significantly different (having checked that that the residual risk here is itself tolerable, do any of the options represent the best use of the safety £ or would money actually be more effectively spent elsewhere to get a bigger safety improvement there?)
RE: 2012 Q7 Signal Sighting - dorothy.pipet - 06-01-2016
Another attempt for comments please
RE: 2012 Q7 Signal Sighting - PJW - 24-01-2016
(06-01-2016, 02:26 PM)dorothy.pipet Wrote: Another attempt for comments please
a)
Very full answer- probably more than you need for 4 marks but great if you can do it within the time as there isn't anything not relevant so only superfluous from a "marks per minute" perspective.
b)
In this particular case should have had a representative from the TOC or whoever responsible for the operation of the station(signage issues, dispatch arrangements). Perhaps structures s well in case a solution may involve a banner mounted on the footbridge or similar.
c) To me the one hazard is a SPAD at HY7 but it can arise in the different ways:
a) driver fails to check signal at all as not clearly visible once doors are closed, so SAS-SPAD (I do not really see distinction between your 1 and 4; I suppose your 1 is failing to check signal at all, your 4 is failing to check that an RA is displayed. I must admit to being pre-conditioned to it being a LU example (the Eastbound and Westbound are a bit of a clue!) and they don't use RA but driver CCTV either through the window or actually displayed in the cab. Your example 4 would be more to do with the placement of any mirro or CCTV monitor in that case, but yes NR may well use RA.
b) driver checks signal but by moving from their seat, then closes the doors and from driving position can't easily see that there has since been a reversion (but of course the route should still be locked, so unless it was replaced to protect an emergency it is difficult to see there is much risk,
c) as you said in your 2: "reading across",
In other circumstances I think you are right re your 3, but here it does seem unlikely that acceleration would be so great as to have a dangerous overspeed at the points.
So I am struggling to see how you get the 4 marks for this portion; I suppose you could mention that an incoming driver may not realise quite how close they need to approach the buffers in order to get the rear of the trai in clear and so could compound visibility problems for return journey and even leave the tail of the train still locking the scissors leading to delay and service disruption, but rather clutching at straws- easily solve by car stop markers in the facing direction!
d)
No issues with what you wrote, except that a splitting banner would solve your issue 3.
I image that it would generally be impracticable but perhaps the terminal platforms could be lengthened (or perhaps a more effective type of retarding buffer-stop may allow a greater length of the physical platform well actually to be utilised.
You made no assumption re the existing level of provision of train protection; one would assume at least "trainstop" type functionality at the signal, but could place another train stop or equivalent on the approach to the signal just ahead of where the nearest cab is expected to be, so as to intervene as soon as there is a move up to a signal at red (wouldn't help your item 4 re the RA observation though). The situation could actually be worse with a more sophisticated form of train protection- given the reversal an the new opened cab, depending on the technology it may not be in full supervision yet!
e)
Yes just seemed to want standard "Yellow Book" type stuff.
The one thing that was obviously missing was to demonstrate that the final risk was actually tolerable not just the best value for money of the two.
You said that both solutions needed to be ALARP, but of course they might not be; one may be disproportionate and provided the other does reduce the risk to a tolerable level (and there are no other ALARP solutions possible) then that is the one to adopt.
Overall I thought this was a good answer, but I a bit surprised of some of the examiners relative mark allocations, which always make one wonder if have missed something....
RE: 2012 Q7 Signal Sighting - Jerry1237 - 26-01-2016
It is good to see train dispatch and station issues being brought up. There have been several recent accidents/incidents regarding public/train interface and dispatching of trains - including a guard who was imprisoned! Signals [at stations] are not just for drivers.
Jerry