Firstly apologies; I overlooked this in the “to do” pile; it was a busy week with after work activities every evening!
615AC
Generally as per 615AM and pretty good, but with similar comments re routing of 688E etc.
Given that it is a Goods Line, I do wonder whether the GK/RT0044 locking against all the routes forward from 645 is really needed; also seems partially to defeat advantage of not providing the main route with an overlap- for following trains it seems that would more quickly be able to get an aspect on 615AM than could even set the route for 615AC. Of course as a candidate there is always the fear that examiners would be looking for that locking, but I think that stating assumption that not needed would have been better (and also quicker).
I would however have stated the route would be selected by virtue of having utilised separate exit button.
Biggest defects concern specific features relating to “call-on”
a) Approach release just shown as BCQ in the “occ for t” column. I’d have written
“BC Q op. w BC” as it would surely also prove the track itself as necessary but insufficient condition to avoid release purely due to treadle depression. I would also added a note in remarks column regarding the need to prove the Approach Release condition not pre-existing for the clearance of signals reading to 615.
b) The expression in the TC clear column is the biggest error; you have written [AB,AC or (AB or AC)] which actually means the same as [AB,AC or AB or AC]. Engage brain- this logical expression is ALWAYS SATISFIED and thus meaningless. I note that in the route level you have correctly specified (AB or AC)occ so why is the aspect level different? If you had not specified the GK/RT0044 locking then I agree that there could have been the chance that the tracks had subsequently been vacated by the first train and thus, having previously set the call-on route, there would have been a need to clear the aspect in that scenario. Even so it would have looked very odd and I’d have written [AB,ACclr ------or----- (AB or AC) occ for 30] which seems reasonable and at least does not look a logical nonsense. Or perhaps combine the AB,AC clr condition with lamp proving of 645 (so effectively reproducing the main route aspect conditions in regard to this area) but exclude from the (AB or AC occ) path. Otherwise you simply have to omit all reference to these tracks and that too looks wrong and so, if showing like that in exam, should add explanatory note why.
c) The opposing route locking specified on yout CT does list or (AC or AB) on the “tracks occ for time” column. Perhaps you felt this implied a non-zero time but as written it similarly looks a bit of a nonsense in the combined expression with previous column. You could have avoided this impression by writing “t” but actually far better to have nominated a time. Given lack of scale factors except as vaguely implied by the line speed etc, then this could have been a purely nominal 30s
615AC
Generally as per 615AM and pretty good, but with similar comments re routing of 688E etc.
Given that it is a Goods Line, I do wonder whether the GK/RT0044 locking against all the routes forward from 645 is really needed; also seems partially to defeat advantage of not providing the main route with an overlap- for following trains it seems that would more quickly be able to get an aspect on 615AM than could even set the route for 615AC. Of course as a candidate there is always the fear that examiners would be looking for that locking, but I think that stating assumption that not needed would have been better (and also quicker).
I would however have stated the route would be selected by virtue of having utilised separate exit button.
Biggest defects concern specific features relating to “call-on”
a) Approach release just shown as BCQ in the “occ for t” column. I’d have written
“BC Q op. w BC” as it would surely also prove the track itself as necessary but insufficient condition to avoid release purely due to treadle depression. I would also added a note in remarks column regarding the need to prove the Approach Release condition not pre-existing for the clearance of signals reading to 615.
b) The expression in the TC clear column is the biggest error; you have written [AB,AC or (AB or AC)] which actually means the same as [AB,AC or AB or AC]. Engage brain- this logical expression is ALWAYS SATISFIED and thus meaningless. I note that in the route level you have correctly specified (AB or AC)occ so why is the aspect level different? If you had not specified the GK/RT0044 locking then I agree that there could have been the chance that the tracks had subsequently been vacated by the first train and thus, having previously set the call-on route, there would have been a need to clear the aspect in that scenario. Even so it would have looked very odd and I’d have written [AB,ACclr ------or----- (AB or AC) occ for 30] which seems reasonable and at least does not look a logical nonsense. Or perhaps combine the AB,AC clr condition with lamp proving of 645 (so effectively reproducing the main route aspect conditions in regard to this area) but exclude from the (AB or AC occ) path. Otherwise you simply have to omit all reference to these tracks and that too looks wrong and so, if showing like that in exam, should add explanatory note why.
c) The opposing route locking specified on yout CT does list or (AC or AB) on the “tracks occ for time” column. Perhaps you felt this implied a non-zero time but as written it similarly looks a bit of a nonsense in the combined expression with previous column. You could have avoided this impression by writing “t” but actually far better to have nominated a time. Given lack of scale factors except as vaguely implied by the line speed etc, then this could have been a purely nominal 30s
(17-03-2013, 11:06 PM)PJW Wrote: Dorothy,
Sorry took longer than I expected to find time for looking at your work.
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I seem to have printed out two copies of the same route and omitted one; its getting late so I'll catch up with the outstanding when I can in the next couple of days. I had a few unanticipated distractions this weekend to deal with- sorry.
PJW
(15-03-2013, 11:34 AM)dorothy.pipet Wrote: Added.
PJW