20-08-2012, 10:30 AM
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Dear Murusegan
Sorry for my slow reply to your posting - Peter asked me to respond, but I was being stupid and have only just found the correct thread!
I have also posted my own "model answer" to this question, but please be aware that this is a suggested, not necessarily unique solution. I have tended to use more of consecutive YY and consecutive Y in my solution, but reading the standards you could equally apply MAR in many of the cases. The MAR solutions effectively require there to be a signal which has correct braking, which can be approach released from red to allow approach to the signal with substandard braking; however in this case, there is often not a "good" signal you can apply the MAR to in the first place!
Signal by Signal comments:
107 at red - correct
111 at red - the distance from 105 at YY to 111 at R is underbraked.
111 at red (ROL) - correct
113 at red - MAR on 111 has been correctly applied to resolve the underbraking (unfortunately 111 is underbraked already, but you can't lose marks for this twice!)
113 at red (ROL) - the examiners will give extra credit for distinguising the different time delays on AAG occupation for the full OL and ROL approaches; in particular, the two appear identical on your answer.
115 at red - it would be better to use the G-YY-Y-Y-R sequence rather than G-YY-YY-Y-R, because of the rule that the distance from first Y to R should be at least one third of the YY-R distance.
117 at red - correct in itself. however, your choice of MAR on 115 now means that there is no use for the YY aspect in 113, so 113 should be 3 aspect - see how the G and YY aspect lines in 113 are joined at both sides.
119(?) at red - correct
junction aspects in 113 - correctly shown. However the line for approach release of 113 from Red is attached wrongly to its Yellow aspect line (a very common error)
Down fast line sequence - all correct, including banner (not named)
In summary, this response has grasped the subtleties of the question, and so is likely to score well in the exam. the opportunity to show that you know the difference between the G-YY-Y-Y-R sequence and G-YY-YY-Y-R
sequences has been missed.
Reuben
Dear Murusegan
Sorry for my slow reply to your posting - Peter asked me to respond, but I was being stupid and have only just found the correct thread!
I have also posted my own "model answer" to this question, but please be aware that this is a suggested, not necessarily unique solution. I have tended to use more of consecutive YY and consecutive Y in my solution, but reading the standards you could equally apply MAR in many of the cases. The MAR solutions effectively require there to be a signal which has correct braking, which can be approach released from red to allow approach to the signal with substandard braking; however in this case, there is often not a "good" signal you can apply the MAR to in the first place!
Signal by Signal comments:
107 at red - correct
111 at red - the distance from 105 at YY to 111 at R is underbraked.
111 at red (ROL) - correct
113 at red - MAR on 111 has been correctly applied to resolve the underbraking (unfortunately 111 is underbraked already, but you can't lose marks for this twice!)
113 at red (ROL) - the examiners will give extra credit for distinguising the different time delays on AAG occupation for the full OL and ROL approaches; in particular, the two appear identical on your answer.
115 at red - it would be better to use the G-YY-Y-Y-R sequence rather than G-YY-YY-Y-R, because of the rule that the distance from first Y to R should be at least one third of the YY-R distance.
117 at red - correct in itself. however, your choice of MAR on 115 now means that there is no use for the YY aspect in 113, so 113 should be 3 aspect - see how the G and YY aspect lines in 113 are joined at both sides.
119(?) at red - correct
junction aspects in 113 - correctly shown. However the line for approach release of 113 from Red is attached wrongly to its Yellow aspect line (a very common error)
Down fast line sequence - all correct, including banner (not named)
In summary, this response has grasped the subtleties of the question, and so is likely to score well in the exam. the opportunity to show that you know the difference between the G-YY-Y-Y-R sequence and G-YY-YY-Y-R
sequences has been missed.
Reuben