08-10-2012, 07:07 AM
Hello Peter,
Yes for me too the surprise was the question on theoretical headway for 3 and 4 aspect signalling which I believe is the first time the exams have asked for this (as far as I know since 2002). From practice of past years' exams, this part could have been completed fairly quickly using Newton's laws of motion to determine stopping and non stopping headway. This new requirement required a few minutes thought (which ate into the 10 mins reading time which for me was to have been used in studying the layout).
I derived this theoretical headway substituting braking distance (2 and 1.5 times braking distance for DGR) to derive the theoretical headway using HW time (now an unknown) x 120 km/h = reaction distance + DGR + overlap + train length. As there was no headway requirement as such, the spacing of the signals was based on junctions that need to be protected. I used a combination of 3 and 4 aspect signalling for the Main and as there was no upper limit to signal spacing usually derived from headway was prepared to schedule them to 1.33S (S being braking distance) or 0.67S.
The other part rquired working out the roundtrip running time (inclusive of dwell times and layover) of a single line train working from B to E again the first time this had been asked although this has been covered in PJW's Study Pack Appendix G. This I could do but felt could have been faster with practice (but never did because it had never been asked before). To be fair to the examiner, he did try to help minimise time by placing the stations equidistant.
So my time taken for the calculations was a bit longer by another 10 minutes at least I think.
Managed to do varying degrees signal positioning on the mainline with transition from 4 aspect to 3 aspect signalling, the freight yard, trap points, numbering of signals and naming of track circuits, a bit of each to demonstrate to the examiner but could not complete all because of a lack of time. For single line working I used No Signaller Token although with hindsight Tokenless Block could also have worked.
For me this year has been my best attempt so far but whether I can do well enough to pass is another matter.
Alex
Yes for me too the surprise was the question on theoretical headway for 3 and 4 aspect signalling which I believe is the first time the exams have asked for this (as far as I know since 2002). From practice of past years' exams, this part could have been completed fairly quickly using Newton's laws of motion to determine stopping and non stopping headway. This new requirement required a few minutes thought (which ate into the 10 mins reading time which for me was to have been used in studying the layout).
I derived this theoretical headway substituting braking distance (2 and 1.5 times braking distance for DGR) to derive the theoretical headway using HW time (now an unknown) x 120 km/h = reaction distance + DGR + overlap + train length. As there was no headway requirement as such, the spacing of the signals was based on junctions that need to be protected. I used a combination of 3 and 4 aspect signalling for the Main and as there was no upper limit to signal spacing usually derived from headway was prepared to schedule them to 1.33S (S being braking distance) or 0.67S.
The other part rquired working out the roundtrip running time (inclusive of dwell times and layover) of a single line train working from B to E again the first time this had been asked although this has been covered in PJW's Study Pack Appendix G. This I could do but felt could have been faster with practice (but never did because it had never been asked before). To be fair to the examiner, he did try to help minimise time by placing the stations equidistant.
So my time taken for the calculations was a bit longer by another 10 minutes at least I think.
Managed to do varying degrees signal positioning on the mainline with transition from 4 aspect to 3 aspect signalling, the freight yard, trap points, numbering of signals and naming of track circuits, a bit of each to demonstrate to the examiner but could not complete all because of a lack of time. For single line working I used No Signaller Token although with hindsight Tokenless Block could also have worked.
For me this year has been my best attempt so far but whether I can do well enough to pass is another matter.
Alex