2005 CTs on 2012 IRSE tables

[dorothy.pipet]

Did this some time ago, and now can't remember whether I felt I'd finished them!
Unfortunately I've not had access tot he scanner at work so this post was held up.
Anyhow - comments please?

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opps, one more.

[PJW]

Started looking at the points; clearly you did not finish 211!

210
Overall pretty good; I accept that you show route locking including the overlap so I don't comment upon that now.

Interested why you showed BC as a conditionally foul TC; personally I wouldn't have done as I'd say that any hand-signalled move over 210R would also be via 211R (indeed historically this is a classic case of point-to-point with 210 being "by 211". Not actually wrong but I think unnecessary. However what is wrong is that when you came to 211 points you didn't show such locking and it is definitely needed there.
Also I note that for 210 you have not considered EM as a conditionally foul track (I suppose depending on where the EM/CN functional joint actually is- always one end or the other in a 6ft crossover, not in the middle as Signalling Plans depict - then it may be clear but the plan does not say and you have not stated an assumption. Again 215 would traditionally have had point-to-point with 210, but this time of the form that 210 locks 215; 215 locks 210 so only one of the points could be reverse at any time.
Therefore you do seem to have been a bit inconsistent.

The reason why it is worth thinking of point-to-point is that this can be a way of ensuring that you catch all the flank point calls and associated route holding. You did get most of it, but didn't include 134A(M). I'd have made this call and lock 210N; first it gives flank to the overlap and secondly it stops locking 210R if that is the way they happen to be should CN becomes occupied and prevent the setting of 127A(M) etc. I have rather lost touch with the latest NR standards; the "making it simple" series of Notice Boards seem to me to be anything but! However I'd still be inclined to make 132A(M) detect 210A Normal in its aspect, to avoid the complications of extra SPAD overrun controls if omitted.

Similarly I think 128A(S) should also set and lock 210N.

Another thing that I'd be thinking of relating to point-to-point is the route holding on 210 after 131A(M); in the traditional world the route locking would always have extended to EM (since if having 215N is a pre-requisite of calling 210R then the locking on 210 might as well extend as far as the locking on 215 would have to). Without point-to-pint potentially 210 could be released earlier on the clearance of CN (as you have depicted)- provided of course that joint is really beyond clearance which takes us back to the earlier consideration of the conditionally foul dead track locking. A good cross check is always see if the route locking on points is consistent with the dead locking and if it is not be sure to analyse if there is a good reason for the discrepancy (there rarely is)

As far as the swinging overlaps are concerned then (at least until the latest "simplification") facing points are typically (i.e. except when there is a "preferred O/L defined etc) left where they happen to lie UNLESS the overlap to which they face is not available. The condition on the call is not therefore the further points being "Set locked and detected"; if the the further points are available to go to the lie compatible with the initial lie of the facing points it is them rather than the facers that are called. The facers are only called to move if the overlap beyond them cannot be set (by definition there must be an available overlap if the facers move because the route which has just set and is doing the calling has previously had to ensure that at least one overlap existed or the signaller's route request would have been rejected.
Hence in the calling column of the CT, the way to express it is of the form:
R>N: 107A(M) w 211N (set & locked only)
and in the corresponding route holding column, the entry would be:
N>R: 107A(M) or 211R (set or free to go).

Of course if 107A(M) set and locked 215N for either of the overlap lies over 210, then it would make the corresponding locking simpler and would not be restrictive; clearly that option would not be sensible to apply in the case of 211 as we have operational need to get 211N with 210N


211
You didn't do much of this and I have commented above about the track locking which it seems you overlooked. Clearly you ran out of time to finish the route calling or start the route locking; given the similarity of the two points then I think concentrating your time on the calling was probably the most sensible use of the last moments of your time.
Similar comment as before re the conditional call by 58B(M) and clearly there were various other overlaps involved- it was a shame that you didn't have the chance to add these at all since you can't get credit for what does not appear at all, yet if you had got all the calls then I think you may have got the lion's share of the marks for this point given the similarity of the route locking with 210.

I'll revisit the route CTs later; I'll look at the points on 2010; after all I have once signed into use an interlocking with no routes at all commissioned but the points available on point switches!

Did this some time ago, and now can't remember whether I felt I'd finished them!
Unfortunately I've not had access tot he scanner at work so this post was held up.
Anyhow - comments please?

---

opps, one more.

[PJW]

Now looked at the routes; comments are:

general
Your general notes did not refer to signal disengaging, neither was this shown on the various route sheets, apart from the #1 on the first route.
Perhaps expand your fist sheet to say that on routes where this not shown, the signal disengaged by the first track in the route being occupied.

107A(M)
You really should have enclosed all the swinging overlap conditions in the availability columns to enclose them all but separate from the 205N; technically as you have written it your expression is only demanding 205N when 201N, 215N since the "or" gives the alternative condition 210R, 211R.
Similar comment for the aspect level, although here you have the end bracket (for association with the $32) but no corresponding open bracket.
Also in this expression you seem to have written 214R rather than 211R.

As when discussing the points, you seem to be treating the EM joint as being beyond the CP but have not explicitly stated this.

107A(W)
Can't see why you have put the (DA or 206R$37) condition in the tracks required clear in aspect level; you did not in the corresponding (M) route.

205/206 are "wide to gauge traps"- seem at first glance to be a set of points but actually the switch rails are not connected together by stretcher bar and each have their own point machine and are operated independently. To go in or out, you need one of the points N with the other R; for trapping you have both points N and you never have both ends R simultaneously.

146A(M)
In the TC occupied for approach release you have written BE,BF and that means both simultaneously occupied. You should have written " BE or BF"; given that this is the only entry in the column then I'll let you off the brackets- had there been an additional entry (e.g. for a PL move also needing the berth TC occupied) then you would have to put in brackets around the approach release expression.

You have stated BE, BF clear to prevent the application of approach locking. Firstly this contradicts your statement on the notes sheet that comprehensive A/L is not provided. Secondly it is a nonsense anyway since these are the very tracks which are demanded occupied to give approach release; hence at least one must be occupied or the signal wouldn't have been able to clear in the first place!

146A(C )
As above re the comprehensive A/L entry.
You did confuse me by writing BA in the release of opposing locking column; I can see that you intended just as a route level track occupied condition, but think better to have shown in the Special column- if nothing else it would have been more obvious if you'd used a spare line below rather than seemingly associating with 145A(M).

158A(M)
I think you got confused with the lie of 213, perhaps just to make your expressions look balanced, but actually 213 is required R when 214N; affects both availability and aspect level.

In the route locking you forgot the shunt 156A(S) just as a "route normal"; you remembered to preset it when 158A(S) set and to prove the GPL off at aspect level, but you forgot to make sure that it wasn't already set as a route in its own right initially when determining route availability.

The other sin was that you failed to look far enough for opposing route locking; 111B(M)has an overlap extending to the BC/AR joint so conflicts with the overlap beyond 144 as a result of 158A(M). Keep your eye out for such in the exam!

As I read your entry in the aspect sequence column you are saying the "signal ahead" in this case is 148; however you have not obviously specified that 144 must also be proved alight. I think we discussed such some time ago when talking about using this style of Control Table; it is easy to forget such things if allow yourself to be led by the design. Again a lesson to keep in mind for the exam.

128A(S)
I certainly do not advise you doing Permissive and Non- Permissive shunts.
Leaving aside any prejudice I may have against these in the real world in general (and Poole-to-Wool in particular!), then from the IRSE exam viewpoint it gives you an extra route to do (for which there is no mark allocation if not shown on the route box). You just don't have the time to waste.
OK where there is no rationale for a shunt being permissive, then give it an overlap and put tracks in the route and overlap if you wish, but where there is reason for the nominated route to be permissive, then just do the permissive shunt- note in the remarks if you like that NR would provide a non-permissive as well and would then cross lock one against the other.
Although 2 of the 3 examiners are younger than me (there is a scary thought) and they are all well aware of the NR practice, I know what they were brought up with and expect; apart from anything else there is little value in them setting a variety of routes and for the (S) to almost be another (M)!

The only other thing on this route- was there a reason for not setting and detecting 214N?

Did this some time ago.....
- comments please?