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2008 Q3 DEGRADED MODE
#1
Our study group In Brisbane looked at the 2008 paper Questions 1 - 4 last Tuesday and would appreciate some feedback.

We would also like to ask whether the answer reflects the time available to answer three questions.

Thanks,
Hitesh, Laura & Johnson.
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#2
(06-08-2010, 12:09 AM)hiteshp Wrote: Our study group In Brisbane looked at the 2008 paper Questions 1 - 4 last Tuesday and would appreciate some feedback.

We would also like to ask whether the answer reflects the time available to answer three questions.

Thanks,
Hitesh, Laura & Johnson.

Q3. Not so easy to assimilate info quickly from ths one- too much condensed text and I think a tabular approach would have been a benefit. I haven't the time now to get a quick overall picture- just remember that the harder you make it for the examiner, the less charitable they are likely to be- they are human afterall.

Further more detailed feedback to follow
PJW
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#3
(06-08-2010, 07:14 AM)PJW Wrote:
(06-08-2010, 12:09 AM)hiteshp Wrote: Our study group In Brisbane looked at the 2008 paper Questions 1 - 4 last Tuesday and would appreciate some feedback.

We would also like to ask whether the answer reflects the time available to answer three questions.

Thanks,
Hitesh, Laura & Johnson.

Q3. Not so easy to assimilate info quickly from ths one- too much condensed text and I think a tabular approach would have been a benefit. I haven't the time now to get a quick overall picture- just remember that the harder you make it for the examiner, the less charitable they are likely to be- they are human afterall.

Further more detailed feedback to follow

I have added a few blank lines and bullets which to me makes it more easily assimilated and it is now clearer how you have answered the question. For this one I have added little material, but have largely restricted myself to inserting some comments on what you have written.

1. You do need to be careful re the word "risk"; I am primarily looking for a "possible accident with potential consequences". I must admit that the questions often seem to expect hazards (see other posts) but if you feel that this is what the question really means then at least be clear that this is how you interpret- PARTICULARLY in a module 1 question.

2. It is always good practice to define the railway environment from which you have gained the knowledge and experience from which your answer is drawn; in this sort of question it is essential.

3. Your example of "degraded mode" wasn't perhaps the best for this question; I think the examiners were intending a solution by which the interface to the driver was a bit different rather than merely the alternative form of train detection. Arguably it is valid but, as you experienced, it is difficult to give a good answer to the question by using it. However you certainly could have done more with it; what prevents it being reset to zero whilst the section is occupied but it is not in operational service and subsequently, when much later the track circuit failure occurs, the section registering clear despite a train in the section because it just happens to be the same type of fixed formation train that regularly uses the line and so the same number of axles have entered as previously left?

I think that the question was more expecting an answer on POSA ( see the attachment etc in the thread re the 2004 module 3 question) or similar substitutionary signalling with limited controls and functionality.


See also the somewhat similar 2005 Mod 1 question


Attached Files
.docx   2008 Module 1 Q3 Degraded Operation Aus.docx (Size: 20.99 KB / Downloads: 155)
PJW
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#4
Could explain what is the meaning of technological fall back system?

likely, we use axle count instead of track circuit failure temporarily. Is it called technological fall back system??

And,

Is POSA technological fall back system???

Thank you.
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#5
(28-09-2010, 03:14 AM)oxfordjack Wrote: Could explain what is the meaning of technological fall back system?

likely, we use axle count instead of track circuit failure temporarily. Is it called technological fall back system??

And,

Is POSA technological fall back system???

Thank you.


Yes if track circuits are the main means of train detection but there is addition some axle counter detection (perhaps just one long section covering the area of many track circuits) then that would be a means of operating the railway in a degraded mode by means of a technological fall-back. The capacity would be much lower than normal, yet trains could stll be operated with the usual high safety integrity.

The POSA aspect is also a technological fall-back system. Here fewer than the normal signalling controls are imposed so there is less than usual safety integrity (since some of the usual proofs are deliberately omitted), but this is compensated to some extent by the operational rules (e.g. one train movement in the area at one time) and primarily the slow speed of the movement. It is also far safer than attempting to move trains purely by verbal procedure which would otherwise be the case.
PJW
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#6
Another attempt for comment please


Attached Files
.pdf   IRSE-Mod1-2008-Q3x.pdf (Size: 957.08 KB / Downloads: 48)
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#7
(04-05-2016, 10:15 PM)dorothy.pipet Wrote: Another attempt for comment please
2008 Mod 1 Q3 DAP

option 1:
In this specific question which was about plain line, the information regarding the locking of points is not strictly relevant.
It might have been more important to distinguish the scenario in which a train may have to be authorised a signal into a known occupied section (e.g. a track circuit prior to the permissive section in a platform, for which the signaller needs supervisor / Ops Control to authorise before they can speak to the driver).

Similarly if the track section is within an overlap, then worth pointing out that there would be two consecutive sections affected (in a different scenario with multiple track failures, then "ticket working over the entire affected length would be instituted instead of the signal section by signal section methodology).

You needed to put a bit more detail about the procedural working. According to the NR Rulebook, the signaller:
a) must be satsfied the entire block section of line is clear (not just the failed track section) and that any level crossings are closed to road traffic (obviously there are no points, but LX could exist on plain line).
b) must apply to appropriate reminder devices (collars)- there could potentially be an opposing move to an LOS even on plain line.  I am not sure it is actually required by the rules, but signallers tend to place a reminder collar on the affected route which I think they do to be a visual indication to them that they need to authorise the succession of trains nd prevents ARS from attempting to set if the track section suddenly becomes clear.
c) must not set the route (the generic rule prevents other parts of the layout being locked up by route locking that is then held by the track failure)
d) must explain to the driver why the signal is to be passed at danger
e) must convey to the driver the identity of the signal to be passed and the place to which the movement is permitted to proceed (generally the next main running signal)
f) must instruct the driver to proceed at caution and particularly warn regarding any level crossing (including automatic crossings of all types including footpath and barrow crossings which will not be operating normally for the movement)
g) must authorise the overriding of TPWS if provided (and indeed any SPAD Indictor)
h) must ensure no other movements could be affected (e.g. by virtue of overrun protection causing aspect reversion- this can generally be prevented by placing a "SPAD Inhibit Short")

The driver must obtain information either from the signaller or an appointed handsignalman passing on those instructions and must be satisfied that they understand what is required (e.g. are they to inspect the line) and how far they can go. 
Although not directly related to this reason for being authorised past a signal at danger, see the recent RAIB report into Godmersham collision with a herd of cows- after the first train had passed through the section without incident, insufficient caution was exercised before resuming normal working.
Note that except for specific areas of which they have been warned and any low speed restriction, drivers are authorised to travel up to 50mph for other parts of the block section (which may be long).

option 2:
Again the discussion of points seems superfluous given the question; however the provision of POSA is of course more appropriate to junction areas than plain line and the truth is that few are actually commissioned.
If mentioning points, then would have been good to have emphasised that POSA proves “wheel path” of infrastructure between entrance and exit of route, but not points in overlap or flank, nor signal aspect and any associated TPWS.

Of less importance but useful for you to know is that there is some functionality to ensure, as far as possible given the scenario in which used, that the aspect is replaced once a train has passed the signal and that the signal in advance has been restored to danger since last used.

Your description should have clarified that where there is a need for the driver to inspect the line (as there would be for the first train as there can be no certainty why the section became occupied- could be a rail break or the consequence of something happening which is now blocking the line), then the signaller must convey relevant information to the driver before clearing the POSA.  However it could just be cleared for Subsequent train once the preceding one is known to have traversed the section.

option 1 risks:
Generally ok, apart from you are still answering the question as if there were points within the plain line section!
Must admit though it is a strange question; if it is really a simple plain line signal one wonders why it wouldn't (at least in 2008) have been plated as passable auto signal; hence that is why I feel it is sensible to assume that there is a level crossing needing protection
Consideration of communication errors should have included the possibility of talking to the wrong driver and perhaps also any "3rd party" such as technicians called to investigate the fault erroneously conveying information to the driver that they should pass the defective signal.
You do mention it in the lst part, but the reduced requirement for the driver to go trackside is a safety benefit as well as seeding things up; indeed the less time a train is stationary the lower chance that other trains will encounter a signal at red as a result (and if that one is not at red then it can't be SPADed!)

option 2 risks:
“protection to the same level as main routes” could have been better worded; whereas the integrity level of the proving is the same, fewer items are subject to that proving of course.
POSA flashers are actually proved (at least one of the two lamps) and if failure of the flasher is detected the signal is extinguished.

final portion:
Agree that the question did need to be answered in relation to capacity rather than train delays; I assume you realised this after initially finishing.   Otherwise well answered.


Summary
think you'd have been judged guilty of not "reading the question" carefully enough but despite this think that you covered the subject well enough to have passed, but discussion of points cost you time without gaining corresponding marks.
PJW
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#8
(28-09-2010, 07:11 AM)PJW Wrote:
(28-09-2010, 03:14 AM)oxfordjack Wrote: Could explain what is the meaning of technological fall back system?

likely, we use axle count instead of track circuit failure temporarily. Is it called technological fall back system??

And,

Is POSA technological fall back system???

Thank you.


Yes if track circuits are the main means of train detection but there is addition some axle counter detection (perhaps just one long section covering the area of many track circuits) then that would be a means of operating the railway in a degraded mode by means of a technological fall-back.  The capacity would be much lower than normal, yet trains could stll be operated with the usual high safety integrity.

The POSA aspect is also a technological fall-back system.  Here fewer than the normal signalling controls are imposed so there is less than usual safety integrity (since some of the usual proofs are deliberately omitted), but this is compensated to some extent by the operational rules (e.g. one train movement in the area at one time) and primarily the slow speed of the movement.  It is also far safer than attempting to move trains purely by verbal procedure which would otherwise be the case.

As a reminder to all - the exam is there to allow the candidate to demonstrate to the examiner they understand principles and their application. Cost and practicality are not the main drivers. So, overlaying ACs on a TCd section is a solution. Would it get past commercial? Probably not. It also potentially reduces the system reliability! However, it is an achievable technological solution that has benefits, especially over verbal control. Don't forget to write assumptions and ensure that anything proposed is reasonable. Stick to the point, be brief but make sure the underlying point is very clear.

Jerry
Le coureur
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