Looking at your Notes sheet first-
Stating that shunt routes require all tracks clear is rather too dogmatic; it could well be a required operational move to get a train from the up siding into a platform which is already occupied by a train- they do have call on moves into them after all. You could say "shunt routes lock overlaps and prove tracks clear to the maximum extent consistent with the operational use envisaged"- but there again one could argue already implied by "current UK mainline signaling practice". One thing worth knowing is that whereas the layout is drawn by a retired signal engineer, the people who mark the papers are all fully aware of current NR practice.
Think your #1 note is useful means of depicting on CTs
Since layout itself states AWS and TPWS not shown, I wouldn't state that "not provided"; rather inconsistent with stated practice! I think you could just take the lead given by the layout, although perhaps better to cover yourself and state instead "AWS / TPWS not shown"
Somewhat confuses the note re point ends by bringing the route level into the sentence; the fact that they have one identity number means that are treated always as an entity for locking. Whereas "real" CTs would list the separate ends when considering their detection, would never do so when considering interlocking functions, so this isn't "exam shorthand". Indeed if there is an SSI boundary and by mistake the locking on all ends isn't checked before issuing a call on one end, then the result is a "Stockley" incident......
Route and Aspect
Another set of CTs where it is obvious that the candidate knows what they are doing; a bit of a rareity I fear.
Hence few comments and most of these are quite picky.
164B(M)-
Meaning of (TAC) not immediately obvious, but you were rather saved by writing it out in full later for 161A(M)
164B( C)-
I am assuming that wi= "with", though I am more used to w= "when", but the meaning is the same. However did actually need something extra here since the treadle is 100m prior to the signal, so a light loco approaching the signal would activate approach release but may then find the aspect reverts to danger when the treadle arm rises a few seconds after last being depressed by its last axle.
Similarly if the signal is not routed initially and a train (even a long one) comes to a stand at 164, the treadle arm may well have risen up since it is improbable that a wheel would be stopped immediately above it; result is the signal wouldn't ever clear.
Hence the condition actually needs to be stored- the treadle has been operated whilst the track was occupied and then remembered until the track subsequently becomes clear. A case for an explanatory # note.
161A(M)-
Sensible to put the note re considering but not calling 254 as flank; you could of course have used a "soft call" and set them if free to go but not lock or detect.
You should however have provided some overrun protection following a SPAD at 157 and maintaining it whilst BL occupied.
147B(M)-
In the availability expression for the overlap, all the points are equal, so should just read [253N, 254N, 255N or 253R]; the "wi" is incorrect here as it suggests only evaluating that 253 is free to go normal when 254 and 255 happen to be normal and does not imply the checking of 254's or 255's availability.
I think you are sensible to use the ROL for the shunt overlap; it is plain daft to give these routes a longer overlap than for the warner- I am not sure what the official NR standard now says but for a long time at least strict adherence would have resulted in that situation.
In the track controls for the swinging overlap, you have made a silly slip regarding the lie of 253 points; obviously the point ought to be detected in the opposite position for it to condition out the track.
However CH is actually also foul of the overlap over 253R unless 254R; you have missed that conditionally foul track.
The A/L timed release of 147 should be 30 secs and I'd also have expected the locking not to be imposed if CR clear; I know you have stated no comprehensive A/L release provided but provision of one track is simple and effective and certainly NR policy which you are claiming to follow.
124B(M)-
You seemed to decide not to show as opposing locking 152A(M) on the basis that there is no overlap via 236R beyond 131. However the train can stop at 131 and the overlap will time out, releaseing the locking on 236. Still don't want to be able to set 124B(M) so that opposing locking was in fact needed after all. Similarly from 156 etc.
Same comment re the approach release using BG Q; since this is even further from the signal than the previous case, the opportunity for signal clearance and thereafter signal reversion is even more likely as things are at present on your CT.
Another thing is that the aspect should be proving that there is no premature release stored for 149; hence FH Q should be proved "not operated" and indeed any stick circuit or timer implementing the aapproach release of 149 should be down proved- similar to Raynes Park control (that is usually shown on NR control tables by $16 against the relevant track).
So pssibly just a few things to learn and tighten up on, but overall another set of CTs to be proud to have shared; I am sure that many other users of this website will gain from looking at your attempts.
I'll try to look at the points tomorrow.
Stating that shunt routes require all tracks clear is rather too dogmatic; it could well be a required operational move to get a train from the up siding into a platform which is already occupied by a train- they do have call on moves into them after all. You could say "shunt routes lock overlaps and prove tracks clear to the maximum extent consistent with the operational use envisaged"- but there again one could argue already implied by "current UK mainline signaling practice". One thing worth knowing is that whereas the layout is drawn by a retired signal engineer, the people who mark the papers are all fully aware of current NR practice.
Think your #1 note is useful means of depicting on CTs
Since layout itself states AWS and TPWS not shown, I wouldn't state that "not provided"; rather inconsistent with stated practice! I think you could just take the lead given by the layout, although perhaps better to cover yourself and state instead "AWS / TPWS not shown"
Somewhat confuses the note re point ends by bringing the route level into the sentence; the fact that they have one identity number means that are treated always as an entity for locking. Whereas "real" CTs would list the separate ends when considering their detection, would never do so when considering interlocking functions, so this isn't "exam shorthand". Indeed if there is an SSI boundary and by mistake the locking on all ends isn't checked before issuing a call on one end, then the result is a "Stockley" incident......
Route and Aspect
Another set of CTs where it is obvious that the candidate knows what they are doing; a bit of a rareity I fear.
Hence few comments and most of these are quite picky.
164B(M)-
Meaning of (TAC) not immediately obvious, but you were rather saved by writing it out in full later for 161A(M)
164B( C)-
I am assuming that wi= "with", though I am more used to w= "when", but the meaning is the same. However did actually need something extra here since the treadle is 100m prior to the signal, so a light loco approaching the signal would activate approach release but may then find the aspect reverts to danger when the treadle arm rises a few seconds after last being depressed by its last axle.
Similarly if the signal is not routed initially and a train (even a long one) comes to a stand at 164, the treadle arm may well have risen up since it is improbable that a wheel would be stopped immediately above it; result is the signal wouldn't ever clear.
Hence the condition actually needs to be stored- the treadle has been operated whilst the track was occupied and then remembered until the track subsequently becomes clear. A case for an explanatory # note.
161A(M)-
Sensible to put the note re considering but not calling 254 as flank; you could of course have used a "soft call" and set them if free to go but not lock or detect.
You should however have provided some overrun protection following a SPAD at 157 and maintaining it whilst BL occupied.
147B(M)-
In the availability expression for the overlap, all the points are equal, so should just read [253N, 254N, 255N or 253R]; the "wi" is incorrect here as it suggests only evaluating that 253 is free to go normal when 254 and 255 happen to be normal and does not imply the checking of 254's or 255's availability.
I think you are sensible to use the ROL for the shunt overlap; it is plain daft to give these routes a longer overlap than for the warner- I am not sure what the official NR standard now says but for a long time at least strict adherence would have resulted in that situation.
In the track controls for the swinging overlap, you have made a silly slip regarding the lie of 253 points; obviously the point ought to be detected in the opposite position for it to condition out the track.
However CH is actually also foul of the overlap over 253R unless 254R; you have missed that conditionally foul track.
The A/L timed release of 147 should be 30 secs and I'd also have expected the locking not to be imposed if CR clear; I know you have stated no comprehensive A/L release provided but provision of one track is simple and effective and certainly NR policy which you are claiming to follow.
124B(M)-
You seemed to decide not to show as opposing locking 152A(M) on the basis that there is no overlap via 236R beyond 131. However the train can stop at 131 and the overlap will time out, releaseing the locking on 236. Still don't want to be able to set 124B(M) so that opposing locking was in fact needed after all. Similarly from 156 etc.
Same comment re the approach release using BG Q; since this is even further from the signal than the previous case, the opportunity for signal clearance and thereafter signal reversion is even more likely as things are at present on your CT.
Another thing is that the aspect should be proving that there is no premature release stored for 149; hence FH Q should be proved "not operated" and indeed any stick circuit or timer implementing the aapproach release of 149 should be down proved- similar to Raynes Park control (that is usually shown on NR control tables by $16 against the relevant track).
So pssibly just a few things to learn and tighten up on, but overall another set of CTs to be proud to have shared; I am sure that many other users of this website will gain from looking at your attempts.
I'll try to look at the points tomorrow.
(28-06-2013, 09:07 AM)dorothy.pipet Wrote: Feedback and comments please?
PJW