2011 Q5 Automatic Route Release

[BHAR6026]

Hi,
I have given an attempt for 2011 question 5 and I am not sure whether I have placed things properly. Please provide review on this.

Thanking you in advance
Madhu

[PJW]

The first 9 lines of your answer was a rather long introduction that said not much.

First bullet- yes TORR requires the signal to be disengaged (i.e. first track in route becoming occupied whilst signal showing proceed and berth track occupied)- would have been better worded like that!

Next section- again wording could have been better; there is an absolute need to have released Approach Locking by sequential track operation (either berth and first or first and second) PLUS one of the following conditions (selected according to which is the most appropriate for the specifics of the site during Control Table design).....
No mention of the possibility of "lookback TORR".
Since there are 13 marks to gain, then I think you need to explain a little more re the circumstances where each might be used(trains dividing, short tracks with fast trains, routes into sidings with few track sections etc.)

I am not quite sure where your answer moved on to the 2nd part; the wording at the top of page 3 suggested that you were still on part 1 (but seemed a bit repetitive) although it could also be intended to be the start of part 2.

# first bullet- don't think so much to prevent TORR if train SPADs, but really to minimise the chances of inappropriate route cancellation just due to track circuit failure scenarios- by ensuring that TORR isn't primed until a train has entered the route it minimises the chance that if a random fault happens to present a sequence to the interlocking that it will be misinterpreted as a valid train movement.
# second bullet- if TORR occurs then the signal would actually definitely not reclear after passage of train as there would be no route set!
# third bullet- if signal set to work automatically then signal will not be disengaged, so really achieved via that rather than explicitly checked,
# fourth bullet - yes, I had expected this mentioned earlier in your answer and you should explain why,
# fifth bullet- yes; again I had expected this earlier
# sixth bullet- yes but should have explained re resetting to TISP0 if the first section used for A/L release doesn't remain constantly occupied before the second is occupied
#seventh bullet- again explain more what is really meant and explain why important

At bottom of page 3 / page 4 (still not completely sure which bit you are answering here) you give the different means of A/L release but in fact for TORR then this won't occur if A/L has been released by time, or by the comprehensive lookback path; it needs to be by virtue of a train having entered the route. This is an important point and by presenting as you have it is obvious that you hadn't appreciated that.

I haven't found anything in your answer that seems to be discussing the appropriate levels of safety integrity applicable to these various elements. This is a shame since without such content, you are really restricting the marks that you can be awarded to those available for the first part of the question and so it is virtually certain that you couldn't get a pass on this question despite the length of your answer and the fact that almost all of what you wrote was true and most of it relevant.

What the examiner was really trying to get you to say was whether all the logic for TORR needs to be performed in the SIL4 vital interlocking or whether some elements could be checked in a lower integrity system such as a Panel Multiplexor and justify this on the basis of the consequences which could result. This is in fact where your opening paragraph might have been better placed and given added value- TORR fundamentally replaces the signaller pulling the entrance button of a signal route so what is appropriate given the worst that could happen?

Hence you are bound to feel disappointed, as I guess that you think that you had done quite well; certainly your answer was of good length, easily readbale, reasonably presented and you seem to know your stuff.
Take this as a learning experience and a warning for the exam- be very careful to read the question carefully and address all of it- this is I believe where many people meet their downfall.

Hi,
I have given an attempt for 2011 question 5 and I am not sure whether I have placed things properly. Please provide review on this.

Thanking you in advance
Madhu