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Answers to 2002 Part A Q1 & Q2 - alexgoei - 05-09-2008
Hello Peter,
Please can you go through my answers for the 2002 paper.
It is quite an unusual paper as there are not many opposing routes and one of the aspect control and route entries involves the use of a ground frame.
Thank you once again for your time and attention. Look forward to your comments.
Thank you & Regards
RE: Answers to 2002 Part A Q1 & Q2 - PJW - 08-09-2008
alexgoei Wrote:Hello Peter,
Please can you go through my answers for the 2002 paper.
It is quite an unusual paper as there are not many opposing routes and one of the aspect control and route entries involves the use of a ground frame.
Thank you once again for your time and attention. Look forward to your comments.
Thank you & Regards
Yes it is a bit unusual.
You are obviously not only doing a significant amount of practice (I wonder how many other candidates are; I see little evidence of it!) but also studying the Past papers for "form" to see what comes up regularly.
You also recognise that there is something unusual most years, be it level crossing or flashing sequence etc. Obviously having considered as wide a selection as possible should increase your chances of being able to deal with such things, but if something comes up that you don't actually know how to deal with DON'T PANIC. The majority of the marks will still be for the usual stuff. Just have a shot (proving both at route and aspect level would be a reasonable thing for things ranging from a shunters release to aircraft trip wire); don't deliberately ignore it- if you have absolutely no idea of what to do then just state that since at least the examiners will reaslise that you are aware that something needs to be done (and in the real world you'd ask someone or find out somehow). Don't agonise about how many marks you'd have lost because it won't be many; just carry on and concentrate on doing the bits that you can do.
Railway double track triangles as that shown are not very common and certainly stations split with platforms on two converging lines are also reasonably rare; the combination may be unique for the mainline railway. I have the feeling that I ought to know the place that inspired this layout. There was a model railway on the exhibition circuit some years back, definitely Midland Railway in the early 20th century, almost certainly Derbyshire / Peak District. It may have been Ambergate; however whereever it was I am sure that it was really quite close to the area of the country where I have been spending the last couple of weekends so that is a bit of a strange coincidence in timing.
You are right that there is no need for opposing route locking, usually such a component of the staple diet, in this area. Note however the routes in the terminal station area do give you enough to demonstrate that you know what you are doing in that department- indeed I think it is quite a good layout having a bit of many things rather than just being heavy with opposing routes as some are.
I am suprised that Ground Frames do not occur more frequently. This one seems peculiar though- I really don't see why it is a GF rather than hand points. Certainly the FPL on 1B is pretty redundant- the only thing that can take it in the facing direction is a light loco leaving the short spur. It is only a trailing point in the passenger line, yet it has been given an FPL which locks in both lies; I have to ask WHY? It could be a handpoint at such a position beyond the end of the platform and on many heritage lines in the UK it indeed is; if theere is a greater length of railways going off to a loco depot or more sidings then there would be a sign at the end of the platform stating "Passenger trains must not pass this notice" and from thereon points would be handpoints. It makes precious little more sense on the runround yard- any train running in will already have passed over set of handpoints. There is also no stop board etc to act as an end of movement authority prior to encountering the point 1A- I suppose the one advantage over handpoints is that it does prevent any train in the loop converging with a loco that may be just off the platform standing on points 1B.
For the exam I think it'd be wise just to prove "Ground Frame locked and detected Normal" at both route and aspect level for any signalled move into either the platorm or the Yard line. (Note that a handsignalled move from the sidings could be made whilst GF released and potentially its points reversed- presumably the fact that 1A is reversed means that any train occupying DM must be in the spur portion .......)
I am just glad that we were not asked to do 217's CT; I really don't know a sensible way of maintaining the locking adequately yet not excessively after 137A(S) or 303A(S) used. If I were drawing the plan and I had to have the GF (perhaps we postualate that the line used to continue and has since been cut short and the pre-existing GF retained) there would be another track cirsuit CL on the Run Round yard and probably a "STOP and Obtain Instructions" noticeboard at points 1A and opposite it at the end of the platform.
However time to consider the CTs you did for the examiners' layout....
RE: Answers to 2002 Part A Q1 & Q2 - PJW - 10-09-2008
Realised that I had not looked at the points for 2002 and thought I'd got myself confused; now I note that you had actually posted as file called 2000 under 2002 heading, so perhaps it is you not me
PJW
RE: Answers to 2002 Part A Q1 & Q2 - alexgoei - 14-09-2008
Hello Peter,
Thanks for reviewing and commenting on my past exam submissions so far.
I have reviewed your comments for the 2002 paper and have some further questions which I have entered the text in red in the appended file.
This is in particular to Comprehensive Approach Locking.
Please ignore the ones highlighted in yellow which are for me to pay attention to.
Look forward to your reply.
RE: Answers to 2002 Part A Q1 & Q2 - PJW - 14-09-2008
alexgoei Wrote:Hello Peter,
I have reviewed your comments for the 2002 paper and have some further questions which I have entered the text in red in the appended file.
This is in particular to Comprehensive Approach Locking.
Please ignore the ones highlighted in yellow which are for me to pay attention to.
Comprehensive Approach Locking does not apply to an MAR = (Approach Released from Red) route; there would be no value. Either a) the signal is at danger since there is no train on the berth track(s) in which case approach locking would not yet have been applied, or
b) the signal is Approach Locked yet any lookback bound to fail- no sense in undertaking the task of go-looking for a train when by definition we already knoww that there is one!
Approach Release from YELLOW (either MAY-YY or MAY-FA) is DIFFERENT. The signal is allowed to clear to yellow (plus route indicator but this goes wiithout saying) before a train is on the approach. The approach release just applies to the "better aspects"; the signal cannot show a double yellow or green (or in unusual circumstances of consequtive junctions a flashing aspect) until the train is closely approaching. Hence Comprehensive A/L DOES APPLY since the signal will become locked once it clears to yellow; if the signaller replaces it to red then we need to fin out whether there was a train that could have seen it.
RE: Answers to 2002 Part A Q1 & Q2 - PJW - 14-09-2008
alexgoei Wrote:Hello Peter,
I have reviewed your comments for the 2002 paper and have some further questions which I have entered the text in red in the appended file.
Your Control Table has no dedicated column, so yes I would put the Overrun protection in the Remarks column. In the past instead of "intelligent SPAD protection" where data looks at a track sequence to determine a SPAD has occurred, the traditional approach would have been to put any "flank tracks" in the TCs clear column (a flank track being any TC that is not in the route / overlap but is between it and signals at danger protecting that reserved path through the layout).
The disadvantage is that a single track failure can prevent the clearance of very many signals and thus require a lot of handsignalling to keep traffic moving; the wole-life safety disbenefits rather outweighting the safety advantage. Also in complicated layouts the flank tracks need to be conditioned out by point lie, or "train going away from conflict" controls. Intelligent overrun protection is equally (or more0 complex and I wouldn't recommend attempting the details- just list the key protecting signals where a SPAD would make the CT's route vulnerable. If you wanted, an alternative place to write would be in the TC clear column; "Flank tracks after SPAD at signal xxx"- but personally if you haven't got room for a dedicated column (useful to act as areminder in the exam of course) then the Remarks column would be where I'd show
RE: Answers to 2002 Part A Q1 & Q2 - alexgoei - 14-09-2008
Hello Peter,
Believe this is the first time we are on line at the same time! Local time now is 1653 hrs Sunday.
Can you explain why there is a requirement for BR or 206R for the CAL for 118?
Thanks
RE: Answers to 2002 Part A Q1 & Q2 - alexgoei - 14-09-2008
Is entering Overrun Protection required as part of the exams as the 202 tables do not have them?
RE: Answers to 2002 Part A Q1 & Q2 - PJW - 14-09-2008
alexgoei Wrote:Hello Peter,
I have reviewed your comments for the 2002 paper and have some further questions which I have entered the text in red in the appended file.
This is in particular to Comprehensive Approach Locking.
The purpose of 114's approach locking is to continue to reserve the route beyond the signal in crcumstances in which a signaller replaces the aspect which a train driver may already have seen or been given information about at an earlier signal.
118 will change from Green to Yellow if 114 is replaced. If a train is on BR then (note distance signal 122 to 118 is only 340m) the driver would be able to see the aspect; hence tracks BP and BR must be included in 114's CAL if:
a) 118 could itself have ever displayed an aspect other than Red (hence check for it being ARAFOAL), AND
b) the train on BR is actually relevant to signal 118 (hence the condiion on 206R that tells us that any train there must be going towards 116 rather than 118). [of course if the read-through situation is bad then to avoid driver confusion signal 118 should have been held to danger unless BP occ or 206N, but that is a different part of the interlocking story]
Obviously we also need to consider the situation when 118 is ARAFOAL but 116 is not and the situation is nearly the same- however given the nature of 116 and the slow speed over 206R then I'd expect 116 to be MAR on AP occupied (see route box re aspects displayed for 122B) and thus could just test 116 to be ARAFOAL, though since have no route box that positively tells us that then taking the CAL back to AP seems better.
RE: Answers to 2002 Part A Q1 & Q2 - PJW - 14-09-2008
alexgoei Wrote:Hello Peter,
Believe this is the first time we are on line at the same time! Local time now is 1653 hrs Sunday.
Can you explain why there is a requirement for BR or 206R for the CAL for 118?
Thanks
1. Interesting the website claims your local time is 19:52; it seems to place you 3 hours adrift. Don't know how it determines what your local time is- whether it is something (too clever by half) in the messages via the internet or whether you failed to set it up correctly when first registering..........
2. Be patient- I think even Aitch would not be complaining re speed of service! I decided to give you answers one by one so you got as soon as I finished them, whilst eating Sunday breakfast. The ones I could do without a diagram were fair enough but I did need to put the plates away before getting the drawings out!! Have posted it now. I wish there was such keenness to get ready for the exams amongst those in the UK ....