(14-07-2010, 07:14 AM)PJW Wrote: It may be a few days before I get the time to comment in detail on the attempt....
Sorry it was longer than I said- partly because of attending to other posts, partly because I thought that others may have commented....
1. I think that the
format works quite well and by restricting yourself to a couple of routes per sheet does give the space needed.
I really do prefer separation of the route and aspect levels rather than being intermixed and some columns such as ppoints effectively being in both, but this is one of the compromises forced by only having finite width of paper and using column presentation so if it works for you use this blank.
I suggest that you ougt to have a general notes sheet as well; for example you have only entered points number and if you mean this to mean that all separate ends are detected then you must record this somewhere; otherwise write in each end on each occasion.
2.
Generally pretty reasonable- certainly legible, clear and neat. Entries fitted into the columns reasonably well
3. You didn't
declare your standards- seems a bit of a mixture of vintages but I suppose Railtrack / Network Rail early 1990s on average. Certainly I realise that you chose not to give shunts overlaps (I think good decision) nor have overun detection.
4.
Opposing route locking:
a) you show some fallaciously such as in 114C(M) after 307C(S) which is not required due to this route holding 215 Reverse until it has left the area of interest whereas 114C(M) requires 215 free to go Normal, so the points give sufficient locking.
b) whereas you showed 114C(M) and 114C(C ) correctly, for some reason you got 114D(M) wrong as you claimed that the route would set after the train using the opposing call-on route had timed to a stand. Since the main aspect requires the track clear, the route locking should prevent the route from setting where there is an opposing train even after it has become stationary.
c) On 133C(M) CT you showed opposing locking from 136; this is not a signal having a route (it is a distant signal) and therefore cannot apply route locking. You were however perfectly correct in that 138/142 read up to 134 and so the area of railway is covered by their locking
d)Your CT for 301B(S) demonstrated what I suspected from some others as well. Leaving aside the fact you overlooked the opposing from 302 signal, you showed the locking time off after 114D© but not after 114D(M)- these must be the same.
The signal which we are trying to set and clear aspect is 301. [#1] You have actually chosen to dictate that this proves tracks clear in the aspect BA and BC. This is potentially feasible (but would not have been my choice) and in that case the opposing locking from either route from 114 should NOT time; there is no value since the aspect will not clear and allowing the route to set would mislead the signaller.
[#2] I think that 301B(S) aspect should only prove CD, BH, AH so that it can be used to join trains together (the local passenger are only 100m long and there is 300m of standage). Hence the opposing locking should time off once the up direction move has been timed to a stand. It does not matter whether the stationary train originally came in on a main or a PL move- that is just irrelevant history now. It is the class of route
being set and in particular whether the aspect proves those tracks clear which dicatates whether or not a time off is needed,
not the class of the opposing one used previously
Also it is important where you place the brackets; by definition the timeout
will almost certainly already have occurred before the call-on class route is even set so must not bridge out too much of the opposing locking or else it will not exist at all.
Therefore write: CK CJ [BC, BA ---- or (BC or BA) occ for 30]
which ensures that until CJ is cleared by the incoming call-on then the shunt cannot be set in the opposite direction.
[Some computer based interlocking technologies actually reset the timer to zero when the call-on is set aand don't let it start again until the route locking prior has normalised, but this is not a general practice.]
5.
Approach Control
You made the M,W and C routes all the same by stating CM occ for 50s. Did you initially check the route box entries. These say that the M is not approach released, that the W is released on CM occ and the S required CMQ being the treadle.
I would recommend that you always consider what you are told but also relate this to the signalling practices with which familiar and should there be a discrepency between them then follow the practice that you have declared but add a norte where needing to departing from the layout info or route box info etc because of that.
To NR practice it is usual for the diverging route to be approach released but not when the speeds are no more than 10mph different. The plan does not state the speed through the pointwork but we do know that the speed through the station is 50km/h and hence reasonable to assume that this means all lines and pointwork (I doubt whether the single and double slips are that fast, but thereagain these are only for shunt routes). Hence I am prepeared to accept that 114C(M) needs no approach release and would follow the route box, having statedthe assumption.
However I don't accept that the W should releas purely on CM since it would seem to be 800m long. Actually it is rather long to time on at all and I might state this, but your value of 50s is certainly far better than what the route box suggested.
I'd also actually agree with you that the A/R for the C would not be very different from the W wth a ROL of 55m, but since the route box explicitly stated CMQ then I would follow the use of the treadle. Actually I would record as:
[(CMQ operated)$10 w CM occ] where $10 = non-replacing in order to respect my practices whilst still following the suggestion within the route box.
If your practices do not utilise treadles then you need to say so, or else the examiner will think you have simply failed to follow information presented to you.
6.
Mind your ANDs and ORs
Be careful re your entries- generaly the logical relationship is AND which can simply be epresented by a dot between entries, but where the relationship is OR then you almost always (unless implicit in the column heading) need to write that in.
For 114C(C ) for example your entry says that the proceed aspect demands CH.CG occupied- you should have written CH or CG.
Similarly for 133A(S) the replacement column states EB.EC clear after EB.EC occ and in that case the signal will remain off until BOTH the berth and first track are simultaneously clear. That s not what is wanted; you need to write the "or".
I know presentations vary, but to me you should also relate this column with th tracks clear column- how many of these tracks are non-replacing until the separate replacement condition becomes satisfied?
7.
Flank
This was pretty good but you need to think about 211 and be consistent for 114C M/W/C. Obviously 212C is required Normal being in route and this automatically provides flank via 212A and 212B. There is no reason why 211 should not be Reverse to allow a train from Platform 4 to access locomotive siding- 212B is giving the protection and there is no "sneak path" bypassing 212A due to the way that this double slip has been numbered.
Similarly 114D needs the protection and thus must set, lock and (generally) detect 212N even though not in line of route
Having now looked at your points CT, I find that you have not been consistent between the route & aspect CTs checking the points for availability and subsequently detecting them compared with the entries on the points CTs re the same routes setting and subsequently locking. You will generally find in the exam that you are asked to write CTs for elements which do interlock each other- put some effort into ensuring that the "different sides of the coin" tell the same story!
8.
Aspect Sequence
I think you fell down a bit of a trap in that 114 is a 3 aspect signal but reads up to 108 / 110 which are 4 aspect signals; do keep your wits about you and not run on auto-pilot.
9.
133A(S)- some specifics
I think you got a bit confused re 107E(M); firstly you have stated this is preset and secondly you have listed in the route normal column. I noticed that you showed GK/RT0044 locking between the 110 and the call-on route reading up to it earlier, so perhaps this is what you were intending here. If that is what you intended then 133A(S) would require route locking tracks BH, AH, CF, DA, DB clear after 107E(C ) but there would be no locking related to 107E(M)
133A(S) would be "when cleared" as the route is approach released; don't condfuse shunt class routes from main signals with shunt signals- there are some subtle differences.
10.
133C(M)- some specifics
Note that the route exit is 137 but th aspect sequence is taken from 135; both 135 and 137 need to be proved alight.
There is no need for approach control; this is it's one main route- check the route box.
For consistency with other examples of where you have shown GK/RT0044 locking then should have entry:
BH, AH, CF, DA, DB after 107E(C ) {somewhat simplified but god enough for IRSE Exam in my view}
11.
301B(S)- some specifics
To modern standards wouldn't have approach control; certainly be consistent because if you demand CB occ to clear the signal then it is rediculous to but CB as required lear in the comprehensive A/L release as it can never be satisfied. This is rather a giveaway that you are learning to fill in boxes on the form , without truly seeing the significance and the examiners will notice this.
12.
Swinging Overlaps
You did the simpler one beyond 108 ok but rather inconsistently you seemed to suggest that there was not a swinging overlap beyond 110. Whereas one could claim that practices do not include swinging overlaps, rather hard to make the argument for one and then not for the other- does just look as if you chickened out as it was a bit harder!
I looked at 114C(M) first and was prepared to accept that you only provided the one overlap when looking at the points, yet I then see some nonsense in the track column. You have written some tracks here but conditioned on point lie as if there were a swinging overlap afterall; but taking the two columns together makes no sense.
You have written {[(AH, BH) or 204N], 204N} and this simply logically equates to 204N.
Whilst I am quite impressed with your Control Table entries generally, this pair of entries tells me that you can't really be understanding the significance here, because if you did you just couldn't have written them like that.
Please be sure to ASK if you don't understand any comment; you need to understand WHY just as much as WHAT entry to make where
I haen't looked at everything and I will come back to review your points, but hopefully the above has given you some pointers. Also compare against
this other attempt posted or
this one or
this one
and the comments made on each.
