alexgoei Wrote:Hello Peter,
Appended please find my answer to the 2005 Part A Q1. Would appreciate it if you can go through it and let me have your comments.
I have two questions which I hope you can provide answers to:
1 What is current Network Rail practice with respect to overlaps for shunt routes. Previous postings on this website suggest Yes to overlaps for shunt routes as well. For Shunt routes do they have full and restricted overlaps?
2 In this paper, the notes on the layout states that "Calling On signals on 131, 144, 145 and 146 are running round only." Could you illustrate these movements on the schematic please? I have some problem visualising these moves.
Look forward to your reply.
Thank you & Regards
Just to let you know that it has been a Bank Holiday weekend in the UK marking the end of the British summer so have been away- I aim to catch up the backlog soon!
1. NR stated current practice is to provide overlaps for shunt routes. However to do so is obviously rediculous when the shunt route does not prove all tracks in line of route clear (since in many cases of a shunct route there is a need to get a train to attach to another or a loco to attach to vehicles). Hence in modern jobs the same shunt route actually exists in 2 flavours; there tends to be an automatic selection based on state of occupancy of one or more track sections and thus either the shunt comes as "non-permissive" either an overlap or "permissive" without one since we know there is a train there. Whereas often only 1 route on the plan there are actually 2 different ones in data and CTs.
However I would NOT advise this policy for IRSE exam;
a) it is more work to do in the time, b) the scheme plan may not have envisaged shunts being given overlaps,
c) the examiners would be keener that you demontrate your understanding of the different nature of shunt and running movements.
Hence firm recommendation is DON'T GIVE SHUNT ROUTES OVERLAPS; state your practice is "late 20th century UK Mainline" or "Railtrack" or "current NR with exception of shunt overlaps and Robust Train Protection".
Don't get hung up on needing to do everything to the latest fashion- this is not what the exam is about. I have made reference to them in some replies because I believe that many read and I don't want to mislead them if that is what they have grown up with. To make it clear: unless CTs to absolute recent practice are your day job and it has become automatic for you, I see no rational reason in the exam for providing shunt overlaps but if the layout really suggests them as an expectation then you should definitely state your practice is not to provide.
Shunts only have one overlap; PL aspect means "proceed as far as the line is clear at a speed at which you can stop on sight of an obstruction, no more than 15mph"- there is no equivalent of a delayed Yellow and it would be a nonsense with that definition. There is certainly no need for an O/L longer than a ROL and thus if providing a shunt overlap use the shortest one that exists on the layout otherwise; i.e. if there is a (W) to same destination then use its ROL for the (S), if not use the normal O/L. You'll not find this written down anywhere but is purely common sense, though some real projects don't display that rare commodity I am afraid!
2. It really is not very clear to me. I interpret as saying loco pulls freight from terminal and leaves train on the Up Branch. Loco detaches and gets PL aspect which permits it to get behind 131 or 145 (even if those platforms happen to be occupied by other trains) so that loco can use the Down Branch Loop to run around and be signalled using 155 and 156 to rejoin and couple before pulling train in Down direction along the branch to A. On its return journey the train would surely be signalled up to 144 put then the PL on 157 used to authorise the propelling back into the terminal. Perhaps we also have to assume that some freight runs to C and thus the exit is easy but the return working has to be signalled up to 157, loco detach and be signalled via 157, 156, 146 to get behind 131 / 145 as applicableto get back onto train on Up Branch Loop before propelling back inside the facility.
I am not sure that the Signalling Plan note is very helpful and I would certainly argue that the PL moves from 144 / 146 in this circumstance should have been designated (S) rather than ©. Indeed since no MARI are provided with the PLs this reinforces my view provision of route indicator for a © was at the time of the paper mandatory though has subsequently been relaxed). I also personally am not very comfortable with M/C routes on passenger railway that are not applicable to passenger trains- to be a run around to join a loco back on its own train is definitely SHUNTING, not a CALL-ON that I regard as applying to 2 different trains that may be joining into one but which may remain totally separate.
Basically I agree with you the presentation is unnecessarily confusing; to provide call-ons rather than shunts and then add a note that effectively states they are used a shunts not call-ons is bizarre. We certainly wouldn't do that on "God's Wonderful Railway" but I think the person who drew the plan came from further north and perhaps their tradition differs and we need to respect all cultural heritage even if it differs from our own.........However we might feel like saying it, it is no longer politically correct to say "There are 2 ways of doing a job, the GWR way and the wrong way".
PJW