I have looked at the route and aspect tables; I'll return later re the points. In general I think they are very good, but I have included some feedback on specific items.
Notes sheet
Definitely worth keeping these on separate sht for the whole set of CTs, so recommend your approach to others.
I like the introductory notes and of course defining any $ note that is utilised later on the CTs.
Careful re the last one though, since there is a swinging overlap and therefore not quite that straightforward in the case of 231 in 113A(M)- there is specific column on the CT for “detect N or R at time of clearance but overridden whilst points can legitimately be swinging”. Also I think I am right that to the most recent standards, NR no longer detects facing points in the overlap, other than to condition out those tracks applicable to the potential overlaps which are not in use.
Also worth stating-
1. you are assuming SSI rather than RRI technology,
2. track circuits rather than axle counter,
3. policy relating to providing / not providing shunt route overlaps- this particular layout suggests provision at least beyond 127. Be aware that overlaps beyond a GPL as an exit signal are a lot more common (traditionally may not have been shown as overlaps but typically there was a 200yard exclusion zone beyond that GPL for passenger movements) than an overlap for a shunt route reading upto a main signal (something that has only really arisen in the last 10 years in standards- therefore really only about 7 yesr in actul commissioned sites). More recent IRSE layouts now typically provide shunt overlaps- however when a candidate is stating the principles they are adopting there can be a conflict between them and the given layout so it is worth stating explicitly- particularly as you have chosen to give an overlap on a goods line, then non provision of shunt overlaps seems rather inconsistent. The problem is that “UK mainline signalling practice” is continually evolving…..
113A(M).
I agree with note #1 but wonder whether worth including at such length. I do see sensible to explain in this case why you included in case examiner had a different view, but I think wording such as
#1: Route locking ensures maintained in circumstances in which 124A(S) is subsequently cancelled, but alternative option would have been to prevent 124’s approach locking releasing once a train en route to it.
Since 138A(M) holds 233R and the locking is held indefinitely even if the pre-set shunt 124 is replaced (beware those working on Western Region E10k relay rooms- this is NOT the case with the traditional “facing shunts”) then the opposing locking after 138A(M) is superfluous.
Not convinced that the “or 231R$37” condition on CJ is doing anything useful; unless 233N$37 then CJ will be replacing the aspect anyway by the entry above. As a tester I prefer the track to be listed only once with whatever the point conditions are, rather than having multiple interrelated entries as you have shown. Actually switch diamonds don’t really offer any flank protection and if a train waiting at 173 then eased back then I think it could come foul anyway regardless of the state of 233. Hence can be better to condition out CJ by a track sequence “CJ occ after CH, CJ occ” rather than via point detection (tend not to use route locking so that doesn’t give reversions during handsignalling / possessions etc)
Missed a foul track for the reverse overlap: (CK or 232R or 231N); don’t see there is any value in calling 232R though.
Aspect sequence does not name the signal ahead- the IRSE’s CT blank does not encourage you to show but I think I would.
No reference to signal replacement condition which I feel should be shown, particularly since you note the auto facility. The IRSE blank however does not provide any specific column so is easily forgotten.
No reference to signaller having different exit buttons for the M and W routes
113A(W)
No comments other than those duplicating the above; even if you didn’t feel need to state only the one ROL then still need the comment about route step-up. Actually I would have enhanced that, stating that step up will occur when a forward route is set and the relevant full overlap would then permit aspect clearance.
129A(M)
#3 I don’t see the need to call 253R. I would regard a 55m length into a sand drag as actually a better overlap than 75m onto the running line- it is not as if 253A are just trap points designed to through the train off the track. Of course at the time the layout was drawn, Goods lines would not have been given overlaps. However because you have written the note, the examiner knows where you are coming from and will mark accordingly- shows the value of stating your assumptions!
You originally showed 158B(S) as an opposing route but then deleted; I think that you should have explained why by stating an assumption, because I would have thought it was needed. Perhaps you are assuming that this route would set and lock 251N which would be sensible, but you have not made this clear.
Despite calling all the necessary flank points, the route is still vulnerable to a SPAD at 127, so aspect reversion once one is detected (or more traditionally just putting in the aspect the flank tracks SE, SF, SG) would be appropriate.
Similar comments as 113 re condition on foul track CJ, non statement of replacement condition etc
Approach release just on BH seems too restrictive- we want to keep the freight train rolling slowly but the driver that close to the signal will have the brakes fully applied and barely moving- it takes significant time to release the brakes on a long freight!. Hence should have included BF or, if we judge that the PLJI not readable from that distance, then BF occ for say 10seconds.
A/L release time not shown after you apparently changed your mind; I guess you intended to reduce to 60s given the route is MAR.
129A( C)
Some of the above comments also apply; you should also have made clear whether (as to modern standards) the signaller is given separate exit devices to select the route class and the relevant track circuit controls included at route level in each case. Again just because the IRSE’s blank CT did not lead you to this, shouldn’t mean that you overlook.
You have shown that “at least one of the tracks AB or AC have to be occupied for 60 sec” for the aspect to clear. If we ignore GK/RT0044 (Huddersfield) locking for a moment- I am not sure that I would provide just for trains into a Goods loop (but I have been out of mainline railways for a while!) then for a call-on we would definitely require the occupancy, but we also need approach release implemented on the entrance signal- in this case BH occupied does seem appropriate as I judge that this may be under 100m long (but worth stating an assumption or writing (BH for 7 secs) to make an allowance for it being a bit longer.
If we then consider GK/RT0044 locking then need to be a bit more explicit re what is a route level control and what is an aspect level, but clearly allowing the signaller to set the route once the first train in in the loop yet holding the aspect level until it is timed to a stand is sensible. Don’t get too hung up on this niceity and then forget the approach release!
146A(S)
Would have been worth stating an assumption / giving an explanation relating to opposing route locking imposed by routes up to 129. Clearly one would expect the overlap locking to be released after train timed to stand so that the junction could be utilised, but I agree there wouldn’t want to be able to set routes such as 146A(S), given the route box stipulation of having 124 off for aspect clearance. If the route setting were permitted one could get situation in which 124 is cleared for a train on BH, route 146A(S) then able to be set and as BH clears then 146 aspect would momentarily clear until 124 then returns back on. Therefore I would agree with your CT entries but it would be in your interest as a candidate to let the examiner know you had thought deeply about it, rather than merely forgotten to time out the locking!
In fact I might be tempted to include BH in the aspect of 146A(S) to avoid such timing problems if we are permitting the oversetting of this route whilst 124 could be off for a previous train.
Again you haven’t mentioned signal disengagement and of course for shunt signals the aspect should only replace once the berth track is clear (unless the train is now occupying more tracks than would be explained by the longest expected propelling move)- this is usually shown as $40 references on tracks on NR control tables with separate entries relating to the disengagement and hold-off conditions. Think you need to decide how to use the IRSE type blanks to depict one way or another.
The A/L should not be imposed if the berth track of a GPL is clear, but you ahve not shown this in the CT.
182C(M)
Should set, lock and detect 261N to give trapping from siding.
I interpret (although it isn’t completely clear) your control table as requiring the 138 route set control in the aspect level of 182 but not in the route level. You have only listed tracks clear up 138; you should have included some more tracks so that there is an aspect overlap (even though the layout plan doesn’t define a route level overlap since the relevant locking is being performed by the following route), so I would have added EA, CJ , BJ, (CK or 232R).
Notes sheet
Definitely worth keeping these on separate sht for the whole set of CTs, so recommend your approach to others.
I like the introductory notes and of course defining any $ note that is utilised later on the CTs.
Careful re the last one though, since there is a swinging overlap and therefore not quite that straightforward in the case of 231 in 113A(M)- there is specific column on the CT for “detect N or R at time of clearance but overridden whilst points can legitimately be swinging”. Also I think I am right that to the most recent standards, NR no longer detects facing points in the overlap, other than to condition out those tracks applicable to the potential overlaps which are not in use.
Also worth stating-
1. you are assuming SSI rather than RRI technology,
2. track circuits rather than axle counter,
3. policy relating to providing / not providing shunt route overlaps- this particular layout suggests provision at least beyond 127. Be aware that overlaps beyond a GPL as an exit signal are a lot more common (traditionally may not have been shown as overlaps but typically there was a 200yard exclusion zone beyond that GPL for passenger movements) than an overlap for a shunt route reading upto a main signal (something that has only really arisen in the last 10 years in standards- therefore really only about 7 yesr in actul commissioned sites). More recent IRSE layouts now typically provide shunt overlaps- however when a candidate is stating the principles they are adopting there can be a conflict between them and the given layout so it is worth stating explicitly- particularly as you have chosen to give an overlap on a goods line, then non provision of shunt overlaps seems rather inconsistent. The problem is that “UK mainline signalling practice” is continually evolving…..
113A(M).
I agree with note #1 but wonder whether worth including at such length. I do see sensible to explain in this case why you included in case examiner had a different view, but I think wording such as
#1: Route locking ensures maintained in circumstances in which 124A(S) is subsequently cancelled, but alternative option would have been to prevent 124’s approach locking releasing once a train en route to it.
Since 138A(M) holds 233R and the locking is held indefinitely even if the pre-set shunt 124 is replaced (beware those working on Western Region E10k relay rooms- this is NOT the case with the traditional “facing shunts”) then the opposing locking after 138A(M) is superfluous.
Not convinced that the “or 231R$37” condition on CJ is doing anything useful; unless 233N$37 then CJ will be replacing the aspect anyway by the entry above. As a tester I prefer the track to be listed only once with whatever the point conditions are, rather than having multiple interrelated entries as you have shown. Actually switch diamonds don’t really offer any flank protection and if a train waiting at 173 then eased back then I think it could come foul anyway regardless of the state of 233. Hence can be better to condition out CJ by a track sequence “CJ occ after CH, CJ occ” rather than via point detection (tend not to use route locking so that doesn’t give reversions during handsignalling / possessions etc)
Missed a foul track for the reverse overlap: (CK or 232R or 231N); don’t see there is any value in calling 232R though.
Aspect sequence does not name the signal ahead- the IRSE’s CT blank does not encourage you to show but I think I would.
No reference to signal replacement condition which I feel should be shown, particularly since you note the auto facility. The IRSE blank however does not provide any specific column so is easily forgotten.
No reference to signaller having different exit buttons for the M and W routes
113A(W)
No comments other than those duplicating the above; even if you didn’t feel need to state only the one ROL then still need the comment about route step-up. Actually I would have enhanced that, stating that step up will occur when a forward route is set and the relevant full overlap would then permit aspect clearance.
129A(M)
#3 I don’t see the need to call 253R. I would regard a 55m length into a sand drag as actually a better overlap than 75m onto the running line- it is not as if 253A are just trap points designed to through the train off the track. Of course at the time the layout was drawn, Goods lines would not have been given overlaps. However because you have written the note, the examiner knows where you are coming from and will mark accordingly- shows the value of stating your assumptions!
You originally showed 158B(S) as an opposing route but then deleted; I think that you should have explained why by stating an assumption, because I would have thought it was needed. Perhaps you are assuming that this route would set and lock 251N which would be sensible, but you have not made this clear.
Despite calling all the necessary flank points, the route is still vulnerable to a SPAD at 127, so aspect reversion once one is detected (or more traditionally just putting in the aspect the flank tracks SE, SF, SG) would be appropriate.
Similar comments as 113 re condition on foul track CJ, non statement of replacement condition etc
Approach release just on BH seems too restrictive- we want to keep the freight train rolling slowly but the driver that close to the signal will have the brakes fully applied and barely moving- it takes significant time to release the brakes on a long freight!. Hence should have included BF or, if we judge that the PLJI not readable from that distance, then BF occ for say 10seconds.
A/L release time not shown after you apparently changed your mind; I guess you intended to reduce to 60s given the route is MAR.
129A( C)
Some of the above comments also apply; you should also have made clear whether (as to modern standards) the signaller is given separate exit devices to select the route class and the relevant track circuit controls included at route level in each case. Again just because the IRSE’s blank CT did not lead you to this, shouldn’t mean that you overlook.
You have shown that “at least one of the tracks AB or AC have to be occupied for 60 sec” for the aspect to clear. If we ignore GK/RT0044 (Huddersfield) locking for a moment- I am not sure that I would provide just for trains into a Goods loop (but I have been out of mainline railways for a while!) then for a call-on we would definitely require the occupancy, but we also need approach release implemented on the entrance signal- in this case BH occupied does seem appropriate as I judge that this may be under 100m long (but worth stating an assumption or writing (BH for 7 secs) to make an allowance for it being a bit longer.
If we then consider GK/RT0044 locking then need to be a bit more explicit re what is a route level control and what is an aspect level, but clearly allowing the signaller to set the route once the first train in in the loop yet holding the aspect level until it is timed to a stand is sensible. Don’t get too hung up on this niceity and then forget the approach release!
146A(S)
Would have been worth stating an assumption / giving an explanation relating to opposing route locking imposed by routes up to 129. Clearly one would expect the overlap locking to be released after train timed to stand so that the junction could be utilised, but I agree there wouldn’t want to be able to set routes such as 146A(S), given the route box stipulation of having 124 off for aspect clearance. If the route setting were permitted one could get situation in which 124 is cleared for a train on BH, route 146A(S) then able to be set and as BH clears then 146 aspect would momentarily clear until 124 then returns back on. Therefore I would agree with your CT entries but it would be in your interest as a candidate to let the examiner know you had thought deeply about it, rather than merely forgotten to time out the locking!
In fact I might be tempted to include BH in the aspect of 146A(S) to avoid such timing problems if we are permitting the oversetting of this route whilst 124 could be off for a previous train.
Again you haven’t mentioned signal disengagement and of course for shunt signals the aspect should only replace once the berth track is clear (unless the train is now occupying more tracks than would be explained by the longest expected propelling move)- this is usually shown as $40 references on tracks on NR control tables with separate entries relating to the disengagement and hold-off conditions. Think you need to decide how to use the IRSE type blanks to depict one way or another.
The A/L should not be imposed if the berth track of a GPL is clear, but you ahve not shown this in the CT.
182C(M)
Should set, lock and detect 261N to give trapping from siding.
I interpret (although it isn’t completely clear) your control table as requiring the 138 route set control in the aspect level of 182 but not in the route level. You have only listed tracks clear up 138; you should have included some more tracks so that there is an aspect overlap (even though the layout plan doesn’t define a route level overlap since the relevant locking is being performed by the following route), so I would have added EA, CJ , BJ, (CK or 232R).
(28-06-2013, 09:09 AM)dorothy.pipet Wrote: Comments and feedback please?
PJW