2012 Q8 - Train Detection Systems

[AdrianM]

An attempt, not under exam conditions so slightly longer than I think I'd be able to do in 30 mins.

Would appreciate input as I found this a tough one to judge exactly what the examiner was after.

Regards,
Adrian

[PJW]

An attempt, not under exam conditions so slightly longer than I think I'd be able to do in 30 mins.

Would appreciate input as I found this a tough one to judge exactly what the examiner was after.

Regards,
Adrian

I thought this was a good attempt; however it no doubt took longer than would be possible in the exam.
There was a bit more than needed on page 1; there were only 6 marks available and this is a module 1 paper with this just being an introduction. I would however mentioned that an axle counter head detects the direction of any movement past it.

I do think that you gave the examiners what they were after. 

b) 2: Worth adding that the potential for a track to Show Clear When Occupied following a feed from the adjacent section due to failed block joint would actually also need another fault (axle would tend to short out the false feed as well the proper one).

b) 9: It might have been better to consider a comms failure between the train and the main control centre as then the interlocking needs to assume the worst case regarding that train's position.

c) 6: This wording evidently reflects, but does nor explicitly state, a scenario when track workers would only be close to equipment during a time when it is signed out of use and within a worksite.

I think that you should have included at least one direct safety risk for CBTC system, for example a position tag being placed in a position that another one should have been placed and vice versa.  The system must be able to identify that the information received from it is bogus, rather than immediately assuming that it is now at the position it has just read from the tag.

It's hard to see what you should have cut out from these later sections to keep within time; I think really that shts 2&3 broadly on, but perhaps shts 4 and 5 could have been abbreviated by removing some detail without losing marks.

[AdrianM]

An attempt, not under exam conditions so slightly longer than I think I'd be able to do in 30 mins.

Would appreciate input as I found this a tough one to judge exactly what the examiner was after.

Regards,
Adrian

I thought this was a good attempt; however it no doubt took longer than would be possible in the exam.
There was a bit more than needed on page 1; there were only 6 marks available and this is a module 1 paper with this just being an introduction. I would however mentioned that an axle counter head detects the direction of any movement past it.

I do think that you gave the examiners what they were after. 

b) 2: Worth adding that the potential for a track to Show Clear When Occupied following a feed from the adjacent section due to failed block joint would actually also need another fault (axle would tend to short out the false feed as well the proper one).

b) 9: It might have been better to consider a comms failure between the train and the main control centre as then the interlocking needs to assume the worst case regarding that train's position.

c) 6: This wording evidently reflects, but does nor explicitly state, a scenario when track workers would only be close to equipment during a time when it is signed out of use and within a worksite.

I think that you should have included at least one direct safety risk for CBTC system, for example a position tag being placed in a position that another one should have been placed and vice versa.  The system must be able to identify that the information received from it is bogus, rather than immediately assuming that it is now at the position it has just read from the tag.

It's hard to see what you should have cut out from these later sections to keep within time; I think really that shts 2&3 broadly on, but perhaps shts 4 and 5 could have been abbreviated by removing some detail without losing marks.

Thanks for the response Peter, hugely appreciated and gives me some confidence that I'm not straying too far away from the examiners question (always a worry!).

I agree that sheets 4&5 could have been condensed. Perhaps with a different layout for part b) (table format) with part c) being the last column, this would have been a better choice.

I definitely feel I'm heading for the A3 answer sheets next Saturday, even if i don't need the room, I hate feeling my answer suffering due to running out of space.

Thanks again.
Adrian