2011 Question 11. Aspect Sequence

[PJW]

Dear PJW/Reuban,

Thankyou very much for your valuable comments, i will improve it.

Regards,

Murugesan

Some further thoughts of what the examiners might have been looking for on this very UK specific detailed question:

1. Some other assumptions that could have been made
- sighting of 113 signal and JI to allow release as soon as train has passed 111.
- non standard sequences (as opposed to MAR) are necessary for headway purposes
- risk associated with non standard sequences is acceptable

2. Ideally the distances of the signals 'off plan' would be quoted (at least the minimum distance and preferably the assumed actual distance - important to ensure both sufficient distance and no 2/3 - 1/3 breach, noting 1/3 of minimum is now acceptable)

3. The MAR - 111 ROL is probably there to allow a train to get closer to the station whilst there is another train stationary in the platform. Similarly 113 ROL would allow a train to enter the station with a train stood at or passing 115. These are provided and you should show them on the aspect sequence chart if you don't want to risk loosing some marks.

4. The reason for the close spacing is likely to be to achieve good headways on a suburban line so the ROLs would assist with this. This also supports Ruben's choice of approach (i.e. YY-YY etc rather than MAR)

We learnt at the exam review meeting that lots of candidates in last year's paper either didn't spot the underbraking or simply ignored it. There is a lesson here - if a question looks too simple it probably is! Always worth thinking how you can get 25 marks for a question, if you can only see 10, you are probably missing something and best to avoid that question.....