[attachment=56]
Indeed please do- or any one else for that matter.
Aspect Sequence
This is good- clear, neat and accurate. Sorry to detract, but I must say that I think it was a pretty easy one compared to most years. The Down direction wold have had the ROL (comes up most years) and the flashing aspect and therefore a bit more meat.
Not much to say about what you did:
a) Having adopted the diagonal lines for the "Green up to Double Yellow or Green", you probably should have done the same for all places where the sequence lines join; this reserves the angular vetical line for the "approach release step" which just makes it all clearer. I am a bit of dinosaur and regret the fact that most charts today go for the pure vertical / pure horizontal presentation for everything just because it is easier for the CAD operator without thought of the usefulness for the end user.
b) Your "end of TC area" beyond 116 is sensible (as strictly speaking no overlap symbol was utilised); the situation beyond 142 is similar but is less clear-cut as arguably there is an overlap back out onto the running line so I'd have been tempted just to denote it O/L and leave it like that.
c) Just a word about the POL beyond 182- the extent of the train detection in the section signal in rear- let's call it 186- would include ED track, as shown by the overlap symbols. The significance of the POL is that it signifies that a train can be signalled up to 182 simultaneously with one up to 173/5. Although there is only one element of train detection between the opposing signals (ED) the OVERLAP is not being shared as each signal has its own distinct required length to the place annotated POL and so no sharing is involved; it is just that this place is not obvious on the ground (being a theoretical concept rather than the site of a train detection boundary). However for an aspect sequence diagram the POL can be ignored- it is the whole of ED being proved clear within the controls of the rear signal. I know of candidates who decided against doing this particularly asy question purely because they were worried what to do about the POL (answer = NOTHING!)
d) The approach release time on CD for 162 approach release is very high. OK we don't know the length of the track and the sighting distance of PLJI versus main aspect but that time value feels like a "time completely to a stand" value. We only need to ensure that driver has passed signal in rear (CD itself proves that) and also that there is no risk of seing the main aspect clear to Yellow without also seeing PLJI; it is possible that it may not need any time but the safest thing for IRSE exam is put a time value such as 15 seconds to delay a bit but not a lot.
e) The question what to show on the sequence chart beyond 138 is "interesting". There is no overlap as such shown on the plan. I'd be reasonably comfortable with this IF 182 demanded 138 off; however it only demands "set". I think we need to decide [SO STATE TO EXAMINERS AS ASSUMPTION] that "set" means not just routed but also "signal not disengaged" and also "approach locking not in process of timing out"- i.e. that we know that the train for which it is set is indeed the one which is approaching it. Even that doesn't totally resolve the issue for 138A(M) as potentially we could two following trainson the same route and once the first is on CJ then 138 could be cancelled and overset for the next train waiting at 182. The only thing that would then be holding the aspect is the first train occupying tracks in the aspect overlap; there will be a place at which it passes beyond those tracks proved in 182 but exactly where this is has to be a guess since it is not depicted. Hence I consider the plan deficient but the exam is probably not the place to be too strident and it has all got rather convoluted for the aspect sequence chart. Hence I think I'd just mark as O/L in the usual manner but add a note "NB. extent of aspect overlap relevant for following train is not depicted on plan but I guess extends to include BJ". This makes it clear: 1) you have studied and understood plan, 2) you can make reasonable assumption, 3) you think plan is wrong but too polite to say so.
Route and Aspect
Blank CT
A good demonstration of the advantages and disadvantages of the column approach. There is not a lot of space to play with and need to consider widths both for content of the cells and the wording for the titles. Very difficult to get best compromise but this is reasonable, though note how some are full whilst others light- however a route having many points R rather than N is always a possibility to be considered. A significant Approach Locking lookback would have been impossible to depict in the column allowed; similarly the swinging overlap would also have been difficult (you missed it!).
I suppose from exam technique viewpoint: for a pass it is most important to rattle through quickly all the basic locking (and ignore any complexity as not worth the time), then this CT does the job but if you adopt be aware of its limitations- personally I would give up the separate sub columns within the points (use suffixes) and also try to save valuable width used for Approach Locking release, perhaps by writing column heading sideways. What you can't get away from with this style of CT is how to specify what controls are in the route level and which in the aspect- so for "real life" I don't like it and personally would have so much difficulty trying to use it that I'd prefer a more 11202 style. However I think you have made the right choice for you so stick with it,b but possibly refine slightly with experience of use.
The heading of the route locking columns is a bit of a mix and match hotchpotch. I suggest for the lower row:
[TC clear] or ([TC occ] [for time]) [after signal operated]
The top two rows should be combined and read
EITHER OPTION 1: Route and Route Locking Normal
OR OPTION 2: Signal At Red And Free Of Approach Locking and locking maintained until
Given exam constraints I think option 1 has advantages!
The one thing I urge is LEAVE SIGNIFICANT SPACE UNDER LAST ENTRY before ruling a line and starting the next route- otherwise when you later discover that you have missed something howon earth are you going to be able to add it?
General
1. Replaced by. You have just entered the "stick" track in each case. Nothing wrong with that per se but the NR standard for about the last 25 years is the use two tracks simulataneously occupied to disengage the signal stick- "berth" and "stick". Would be particularly important if there was TORR. If you are claiming "modern NR standard" then I think you should adopt.
2. Oposing route locking. Generally OK but not completely secure- you have missed some "indirectly opposing" yet have put route locking that is not actually required since it is locking a set of points in the last track prior to the relevant signal- the point availability is sufficient to prevent to route from setting. Similarly the extent of the route locking and the "timing off" isn't always right and is certainly often incompatible with the tracks being proved clear in the aspect of call-on or shunt signals. Sometimes the locking of an opposing move has been taken onto the berth track of the signal for which doing the CT- the locking would be preventing a train being routed as it would consider itself to be an opposing movement!
There are various other detail issues and I am thinking how best to feedback; I have just remembered another of my dislikes of this style of CT- no spare space anywhere to right in omissions or corrections!
So that'll have to wait until another evening, but provided you crack the route locking most of the rest of the basics are ok. I am impressed that you saw the need for routes to get themselves trapping from 238 as well as 235 (though you needn't have worried re 236- but apart from minor reliability impact that does no harm).
NOW ADDED ATTACHMENT FOR 113AM
regards,
PJW
alexgoei Wrote:I will go through your explanation and if I need further clarification can I get back to you please?
Thank you once again and I look forward to your other comments
Indeed please do- or any one else for that matter.
Aspect Sequence
This is good- clear, neat and accurate. Sorry to detract, but I must say that I think it was a pretty easy one compared to most years. The Down direction wold have had the ROL (comes up most years) and the flashing aspect and therefore a bit more meat.
Not much to say about what you did:
a) Having adopted the diagonal lines for the "Green up to Double Yellow or Green", you probably should have done the same for all places where the sequence lines join; this reserves the angular vetical line for the "approach release step" which just makes it all clearer. I am a bit of dinosaur and regret the fact that most charts today go for the pure vertical / pure horizontal presentation for everything just because it is easier for the CAD operator without thought of the usefulness for the end user.
b) Your "end of TC area" beyond 116 is sensible (as strictly speaking no overlap symbol was utilised); the situation beyond 142 is similar but is less clear-cut as arguably there is an overlap back out onto the running line so I'd have been tempted just to denote it O/L and leave it like that.
c) Just a word about the POL beyond 182- the extent of the train detection in the section signal in rear- let's call it 186- would include ED track, as shown by the overlap symbols. The significance of the POL is that it signifies that a train can be signalled up to 182 simultaneously with one up to 173/5. Although there is only one element of train detection between the opposing signals (ED) the OVERLAP is not being shared as each signal has its own distinct required length to the place annotated POL and so no sharing is involved; it is just that this place is not obvious on the ground (being a theoretical concept rather than the site of a train detection boundary). However for an aspect sequence diagram the POL can be ignored- it is the whole of ED being proved clear within the controls of the rear signal. I know of candidates who decided against doing this particularly asy question purely because they were worried what to do about the POL (answer = NOTHING!)
d) The approach release time on CD for 162 approach release is very high. OK we don't know the length of the track and the sighting distance of PLJI versus main aspect but that time value feels like a "time completely to a stand" value. We only need to ensure that driver has passed signal in rear (CD itself proves that) and also that there is no risk of seing the main aspect clear to Yellow without also seeing PLJI; it is possible that it may not need any time but the safest thing for IRSE exam is put a time value such as 15 seconds to delay a bit but not a lot.
e) The question what to show on the sequence chart beyond 138 is "interesting". There is no overlap as such shown on the plan. I'd be reasonably comfortable with this IF 182 demanded 138 off; however it only demands "set". I think we need to decide [SO STATE TO EXAMINERS AS ASSUMPTION] that "set" means not just routed but also "signal not disengaged" and also "approach locking not in process of timing out"- i.e. that we know that the train for which it is set is indeed the one which is approaching it. Even that doesn't totally resolve the issue for 138A(M) as potentially we could two following trainson the same route and once the first is on CJ then 138 could be cancelled and overset for the next train waiting at 182. The only thing that would then be holding the aspect is the first train occupying tracks in the aspect overlap; there will be a place at which it passes beyond those tracks proved in 182 but exactly where this is has to be a guess since it is not depicted. Hence I consider the plan deficient but the exam is probably not the place to be too strident and it has all got rather convoluted for the aspect sequence chart. Hence I think I'd just mark as O/L in the usual manner but add a note "NB. extent of aspect overlap relevant for following train is not depicted on plan but I guess extends to include BJ". This makes it clear: 1) you have studied and understood plan, 2) you can make reasonable assumption, 3) you think plan is wrong but too polite to say so.
Route and Aspect
Blank CT
A good demonstration of the advantages and disadvantages of the column approach. There is not a lot of space to play with and need to consider widths both for content of the cells and the wording for the titles. Very difficult to get best compromise but this is reasonable, though note how some are full whilst others light- however a route having many points R rather than N is always a possibility to be considered. A significant Approach Locking lookback would have been impossible to depict in the column allowed; similarly the swinging overlap would also have been difficult (you missed it!).
I suppose from exam technique viewpoint: for a pass it is most important to rattle through quickly all the basic locking (and ignore any complexity as not worth the time), then this CT does the job but if you adopt be aware of its limitations- personally I would give up the separate sub columns within the points (use suffixes) and also try to save valuable width used for Approach Locking release, perhaps by writing column heading sideways. What you can't get away from with this style of CT is how to specify what controls are in the route level and which in the aspect- so for "real life" I don't like it and personally would have so much difficulty trying to use it that I'd prefer a more 11202 style. However I think you have made the right choice for you so stick with it,b but possibly refine slightly with experience of use.
The heading of the route locking columns is a bit of a mix and match hotchpotch. I suggest for the lower row:
[TC clear] or ([TC occ] [for time]) [after signal operated]
The top two rows should be combined and read
EITHER OPTION 1: Route and Route Locking Normal
OR OPTION 2: Signal At Red And Free Of Approach Locking and locking maintained until
Given exam constraints I think option 1 has advantages!
The one thing I urge is LEAVE SIGNIFICANT SPACE UNDER LAST ENTRY before ruling a line and starting the next route- otherwise when you later discover that you have missed something howon earth are you going to be able to add it?
General
1. Replaced by. You have just entered the "stick" track in each case. Nothing wrong with that per se but the NR standard for about the last 25 years is the use two tracks simulataneously occupied to disengage the signal stick- "berth" and "stick". Would be particularly important if there was TORR. If you are claiming "modern NR standard" then I think you should adopt.
2. Oposing route locking. Generally OK but not completely secure- you have missed some "indirectly opposing" yet have put route locking that is not actually required since it is locking a set of points in the last track prior to the relevant signal- the point availability is sufficient to prevent to route from setting. Similarly the extent of the route locking and the "timing off" isn't always right and is certainly often incompatible with the tracks being proved clear in the aspect of call-on or shunt signals. Sometimes the locking of an opposing move has been taken onto the berth track of the signal for which doing the CT- the locking would be preventing a train being routed as it would consider itself to be an opposing movement!
There are various other detail issues and I am thinking how best to feedback; I have just remembered another of my dislikes of this style of CT- no spare space anywhere to right in omissions or corrections!
So that'll have to wait until another evening, but provided you crack the route locking most of the rest of the basics are ok. I am impressed that you saw the need for routes to get themselves trapping from 238 as well as 235 (though you needn't have worried re 236- but apart from minor reliability impact that does no harm).
NOW ADDED ATTACHMENT FOR 113AM
regards,
PJW