2009 Q8 RISK ASSESSMENT OF WRONG DIRECTION RUNNING

[Hort]

Hi,

I have attempted question 8 of Mod 1, 2009. I would welcome any comments.

G

[PJW]

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?

[Hort]

PJW,

I can see the errors I made in interpreting the question, however, I did find the question ambiguous. I was aware that my interpretation might not be correct hence the reason why I stated my assumptions before starting the RA.

If the sentences you referred to had read

[PJW]

[quote='Hort' pid='1626' dateline='1276249699']
PJW,

I did find the question ambiguous....

If the sentences you referred to had read

[Hort]

I have had another go at the question.

Any comments would be appreciated.

[PJW]

I have had another go at the question.

Any comments would be appreciated.

You are certainly considering the correct scenario this time.
You have some appropriate hazards and have values for likelihood and severity, then calculated the risk scores.
You have a list of mitigations and related these to the hazards and calculated revised risk rating, so from that point of view I thought it was great.

I wasn't convinced that it made sense to calculate "risk change"; it suggests that the value has actual numerical significance rather than just being a relative weighting.

I think you must have been assuming (but never stated) that each mitigation was considered in isolation. Take hazard 3 for example: original likelihood 3. You have three mitigations: one of which actually makes no significant change, the second reduces severity and the third reduces likelihood. Obviously if you were implementing them all then you'd have a reduction both of likelihood and severity and only have one revised score for the hazard.

My main concern with your answer was that the question scoring is
Carry out a risk assessment of all aspects of the operation including maintenance and the operation of infrequent wrong direction movements. [16 marks]
Briefly identify possible mitigations for the risks that you identify. [5 marks]
You gave more on the mitigations (it said "briefly identify", 5 marks) than the risk assessment (it said "carry out", 16 marks).
I think that your table should have been simplified by making the second column more of a list (certainly no more than 2 lines of text) and just an indication in the next two columns whether it was to rduce likelihood or severity or both. I think giving revised scores wasn't called for, so save the time. You couldn't have done this page in 6 minutes I think!

Conversely you ought to have spent about 16 minutes on the risk assessment, so the examiners were looking for more. I think that I would have done it much like you, but where there was a hazard such as 1 = SPAD then I'd have split that horizontally into 1a and 1b, the first when reversible working is not in use and the second when it is. This would make it clear that you were considering the two situations.

You say for item 5 that the risk to maintenance staff is higher when using a line in the wrong direction is increased; I agree with you that it is whilst that situation exists. Let's say that it is increased tenfold; however is it likely that reversible routes will be in use for as much as 10% of the time? So which is the biggest risk over the period of a year?

I think that you had a reasonable range of hazards - lack of adhesion, loss of train detection, driver overspeeding, driver failing to respect stop signal, maintenance workers inadequately protected from train movements etc. so what other ones could you have included?

The bit of the question that you haven't incorporated is No train protection system is provided for the reverse direction movement nor is there any suppression of the right direction
train protection.
I do have a bit of a problem with this, thinking in NR context. Obvious form of train protection is TPWS- the frequencies of the loops makes this inherently directional so a wrong direction train won't get tripped- it doesn't need "suppression". Similarly Eurobalise, there is an inherent directionality between the two in a balise group. I am not an expert on the various ATPs but I believe the beacons are offset to the track centre line and they get directionality in that way and again don't need suppession. That only leaves AWS which I don't regard as train protection; I think I need to state this as an assumption to the examiners but then consider the lack of AWS suppression. So the hazard is that the driver gets used to cancelling the bogus AWS warnings whilst travelling on the wrong line and then carries on doing so when regains the right line.

I think that it is reasonable to assume that a line like this may have some level crossings, so perhaps that gives another hazard we can include.

I'd have made more of the loss of train detection. If there is a track bob then we could loose all the rout locking ahead of the train and a route could be set in the opposite direction. The most likely scenario is whilst train traversing those crossovers that may be very rusty from infrequent use. Mitigations might be eucleptic welded strip on the crossover rail surface and specially slow-to-release route locking for the overall totality of each reversible section (proving all track circuits for whole length between crossovers simultaneously clear for say 10 second, before permitting reversal of directionality of use).

We could perhaps consider where the signals for the wrong direction signal would be situated; perhaps they are straight posts on the righthand side of the line rather where the driver would normally expect to see them, so perhaps this would increase the risk of them being SPADed.

Could it be that because of line curvature that a driver on a train running on the normal line might see the wrong road signal first? Given that the ones approaching crossovers are only Y/G signals then there default aspect is yellow which is a proceed aspect. Driver who had receiverd Y on previous signal might think that the signal he is approaching has since cleared and cceases braking but then the R comes into view and travelling too fast to stop at it.

What about the risk of a driver travelling in the wrong direction sees a Green on the protecting signal for the crossover but failing to appreciate that it is for regaining the correct running line and therefore encountering the points too fast. Yes you had considered overspeeding here as a risk, but not really this scenario.

Other than that I can't think of other obvious omissions specifically to do with reversible working; the question certainly asks for operation in normal scenario as well but since is bascally a two line uni-directional railway then there really isn't much- a few causes of a SPAD leading to a rear end collision and you have these.
Perhaps we could include things like track failures, points failure so that we are also considering degraded mode working. Perhaps we could extend this to consider planned engineering works on ne line with a reduced train service on the other. Basically I am struggling now to get more for this section; I don't think I have missed anything so I guess that the examiners are wanting this sort of thing.

Overall this was a reasonable attempt,
however-
far too much intro for which there would be few marks,
very light on the miiddle section where the majority of the marks are, and
more than you could spare the time for in the last section

------------------------------------------------------------------------
A small point (at least re this question and this module is concerned). Some of what you wrote re signalling principles etc was a bit dodgy. I don't think it would have harmed you significantly in gaining marks in this question, but in other cases it would. [e.g. Double Red- the outer signal (you said "in advance" when you meant "in rear" or as we should say now "on the approach" clears once the train has passed beyond its OSS and therefore the train may be some 400m prior so certainly not at a stand]

[PJW]

[quote]
I know it

[Peter]

[quote='PJW' pid='2223' dateline='1285791373']
[quote]
I know it