2002 Layout CTs

[PJW]

Hi, I suggest we can view the other's work and try to give some suggestions before Peter have time. Although we are not professional, reading others' assignment is also good for improvement.
I will read yours first and reply later

I like the spirit - have a look and ask the person why they did the bits that you don't understand and they can explain their thinking and both will benefit!

Commenting on each other's work is certainly a good idea worth encouraging, but to break the slilence I'll make some comments now on certain routes only.

It is also worth comparing with the previous thread which utilises the "column" blank rather than a "sheet per CT blank"

First a general item: I think you ought to define points N or R in the signa; clearance level as well as the availability at the route setting level- ok it can be inferrred but for the time that it takes to do, then I wouldn't risk omitting.

303A(S)

1. The GF release should be npted in the Special Controls column of the route level since it is not "availability"; it has to be locked Normal for the route to be able to be set.

2. In addition the detection of the Ground Frame lever (and if applicable the actual point ends themselves) must be proved at the signal clearance level; this can go in the proved set/locked/detected column.

3. The opposing locking from 138/142/144 should only list tracks up to and including DJ; the train on DHis behind 303 and the role of this signal is to set the train back into a different platform etc- your locking prevents this!
Also you missed track DK when coming from 138.
You missed 144 completely. Actually you might have chosen that 303A(S) set and locked (even if not detect) 216N as pseudo point-to-point by any route over 215R; had you done this then there would still have been a need to include the opposing locking in this instance since 215/216 would free up with train in Up direction on DJ but in other instances may have actually cobvered the locking requirement.

4. For some reason your CT blank for this route is vice versa- you appear to have crossed the tracks clear and tracks occupied headings.
I think it is sensible to prove DJ, DK, CK clear but you have not qualifiedany with a $40 reference, even though you have specified the $40 inhibition correctly in the later column. Need to make an assumption re the length of the propelling move into the run around; if we assume that it is the length of a train that was previously in the platform then we would need to enter
[DJ, DK, CK]$40. If weathall we'd be doing is taking a single vehicle such as the guard's brake van and propelling it with a loco through the run round yard into the headshunt, then [DJ, DK]$40 CK would be appropriate; ideally it is always good to have one "replacing track" if possible so that a signal can't be held off indefinitely as a result of a single IRJ failure.
Note that the $40 convention is an alternative way of specifying the replacement condition than the entry that Alex made; do one or the other but don't get the two confused. He actually chose just to make DJ non-replacing- this would be applicable for a locomotive vbeing driven from the cab at the left hand end and thus just the length of the loco which is being propelled.

5. To modern standards a GPL would not generally be approach released, so therefore there wouldn't be a DH occupied entry at the signal clearance level, similarly a GPL would normally be made comprehensive and thus A/L release isf the berth TC clear and hence I'd have expected DH in the left hand column at the bottom. To older standards however, what you have written is not wrong; it is however a bit inconsistent with the presentation of the two track sequential A/L release which suggests SSI standards.

142A(M)

1. 142 only has the one route; you confused me by claiming 142B(M)

2. At the route level the requirement for (212N or 212R) availability makes no sense; it will always be satisfied, with the exception of SSI interlocking start-up where all points are undefined and this sort of logic is not depicted on Control Tables. Hence the entry should be omitted; if however you decided that for the overlap over the fixed crossing it would be appropriate to set 211R (there is no flank move but is no disbenefit operationally and does get rid of CE as a potential foul track circuit, so might perhaps be something sensible to do) then the availability condition would become: (212N or 212R, 211R) and that does mean something and would be included.

3. The opposing locking after 303B(S) is only DJ, DK; as you have designed it a train that has entered the platform from 303 can never leave!
Conversely you omitted the opposing from 137B; if that train is still going towards the platform on DK track then 213 is free to go Normal and you need the opposing route locking to stop 142 route from setting until train has got totally behind 142.

4. At the signal clearance level your entry for the points (given the general comment at the begnning) was ok; even if you had decided that the route should set and lock 211R then it would probably be sensible to exclude detection, so if adding it in the most lefthand column here then would need a note = "not detected" against it and indeed it would need to be associated with the 212R scenario only.

5. Thinking about the tracks, you are right that the only time when you should be excluding CD is when 212N and 211R- i.e. the overlap is directed away from it and we are also convinced that it isn't occupied on the portion which could be foul. An alternative (and possibly better in these circumstances) means of conditioning would be use a track sequence rather than the detection of 211; you couldd write: [CD except after CBocc,CD occ] as this means that a train at 113 that accidentally rolls back a bit when attempting to start away and thus dropping CD would replace 142 whatever the lie of 211.
With the overlap over 212R then you should also have considered CE as a potentially foul track and have conditioned that by 211R detection (unless you had decided to have set locked and detected that point R anyway).

6. I note that you put flank tracks in as simple overrun detection- it was worth the note to explain the rationale. We tend to make overrun detection more complicated nowadays, but I think this is fine for IRSE Exam and this layout is such that really do need something.

5. It was good that you realised the need to prove both 134 and 136 alight, but not really sure what you intended from your aspect sequence entry. You should have shown the sequence G up to 136 at Y and also G up to 136 at G; you could have recorded the need to prove 134 alight in the remarks column instead which would have saved the confusion.

I'll leave the other routes for a bit and see if you get other comments ....