(09-06-2010, 11:00 AM)Hort Wrote: Hi,
I have attempted question 8 of Mod 1, 2009. I would welcome any comments.
G
Diagram
Signals are spaced approximately every kilometre and the line is equipped with automatic train protection.
Sketch states signals every 15km.
No indication or note re provision of train protection, its type etc.
The line is fitted with double cross-overs at 10km intervals
permitting running moves from the normal running line to the other line in the wrong-direction and back again.
Sketch shows a scissors crossover; I would have assumed separate facing and trailing crossover, but OK. Not signalled for running moves (or even shunting mobes come to that).
Each line is signalled for reverse direction moves but signals are only provided to protect thecross-over points; these signals are provided with distant signals.
Sketch only shows signals for left hand running (only right direction moves); these have no obvious route to the opposite direction track. The stop & distant type of signalling described in the question for the "bang road" has effectively been drawn for the "right road", except for the fact that there would be signals only on the approach not also just beyond the crossovers.
No train protection system is provided for the reverse direction movement nor is there any suppression of the right direction train protection.
Since none is shown at all, can't say much about this!
Sketch this arrangement for a representative 15km section of the railway.
Sketch only depicts one crossover position; I am sure the intention was that two were shown 10km apart and 2.5km approach at either end to show the complete picture of how a train would cross across onto one line and then cross backagain later. I don't deny that a 15km length could be selected that basically extends 7.5km each way from the one crossover position but:
a) this is not a lot of value with the two bits of plain line at either end; I think a bit of "domain knowledge common sense" should tell you that,
b) diagram has no idea of scale but presumably braking distance would be around 1km, so it doesn't really look as if you have drawn a 15km length.
Hence the diagram certainly doesn't convince me that you have read and completely and accurately understood the scenario.
Risk Assesment
It seemed to start well but rather too much information regurgitated from Yellow Book in general description before actually doing what was asked re carrying out risk assessment. However I definitely do think that you were right to have some intro and the words of the first paragraph of your text were fine- the tables were more than what was needed and the essentials could have been incorporated by some slight addition to your initial text-
viz: For each hazard identified the likelihood (scale 1=improbable to 5=frequent) and consequence (scale 1=minor injury to 5 = multiple fatalities) are individually assessed against set criteria and given the relevant score.
It is clear from your next explanation of your assumptions that you certainly have misunderstood the scenario. At least by stating this the examiner will understand upon what your subsequent table entries were based. However the fact remains that you aren't really answering the question set; I am sure that you will pick up some marks for your approach wjhich at first sight seemed to be very good, but obviously answering the wrong question will severly limit the marks that could be awarded.
Basically you answered assuming hand-signalled moves for the train to use acrossover in order to go back from whence it had come; the question was about using signalled moves to permit the train to continue in in its same direction of travel but for a certain length utilise the other running line contrary to its normal traffic to be able to overtake a failed train or to permit planned engineering work.
Summary
If only the question had actually been what you took it to be, then I think that you'd have done very well. Certainly considered a range of items and covered both normal and the degraded mode operation. Perhaps given the marks avaiable you spent too much time on mitigations compared with the hazard risk assessment.
Hence I think that the examiner would feel very sorry for you as you evidently could have done well; whereas the might therefore be a bit charitable there are limits to how generous they can be when a candidate answers the wrong question. Where someone does misunderstand they do revisit the wording of the question to see whether it really was ambiguous and if they find that they can comprehend the candidates interpretation then they will mark the answer on that basis. However in this case there is a lot which is actually very clearly expressed but that you simply haven't followed- cast your mind back to the comments raised relating to the sketch. I just can't twist the wording of the question to match your answer- therefore I'd have to mark accordingly.
As I understand it, it is not unusual for candidates in the actual exam to misinterpret the question in such a way. It probably occurs for a variety of reasons;
a) sheer exam stress- one person who has struggled with the exam over several years has described their "brain becoming like unwound spaghetti" and unable to think clearly
b) a moment of carelessness when reading question and over eagerness to start writing, jumping to a quick conclusion and not challenging self enough. Moto: Measure twice; cut once.
c) subconsciously twisting a question to be what they thought might come up- reading what they thought it said
d) lack of domain knowledge / experience so unaware of the scenario being presented and therefore coming to the conclusion that it must be about the nearest thing which which theey are familiar
e) deliberately attempting to "fob-off" the examiner by a politician's answer wishing to evade the question posed and answer one that they wished they'd been asked instead
It would be useful to understand from you whether you now recognise that you made an error and if so, why you think that it might have been. Presumably it won't be a) or e) in this case; I suppose from little I know that I'd guess a combination something like : b 20%, c 30%, d 50%, but you'd be the better judge.
One reason why it is important to analyse it is to be able to minimise the risk of occurance at the exam. Perhaps we might rate the severity of an exam failure at 2 or perhaps 3; for module 1 the probability of failure statistically has been around 66% in recent years which would rate as 4- hence need some mitigations! Obviously the better idea of the factors leading to susceptibility for misreading, the better the chance of being able to address these prior.
Possibly you are kicking yourself over this misinterpretation- DON'T- no harm done and a good learning experience. Also remember that in overall approach as an answer to this question it was good in length, presentation and much of the content.
Do you want to revise your answer based upon a correct understanding of what you should have been considering?
PJW