2008 Q3 DEGRADED MODE

[hiteshp]

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.

[PJW]

(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]

(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

[oxfordjack]

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.

[PJW]

(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.