Signet17 pre-event Q8 Platform sharing

[PJW]

One of the popular (although not necessarily the best attempted) questions was this one regarding platform sharing. Since it was selected, it has become more topical with the publication of the RAIB Report into the collision at Plymouth.

On the Saturday afternoon at the event, we discussed many of the component parts from which to construct an answer (after having looked at some photographs and diagrams to trigger conversation) but had no time left actually to construct an answer from these.  Hence I have taken one of the best pre-event answers (selected the typed on rather than handwritten just because made it easier for me to modify, tough both had their merits) and have rewritten certain bits to further improve.  However I have left a few items in identified by changing to red strike-through text) to show that these items were not strictly relevant (e.g. asked for "special" and things listed were in no way special in the context of the question so would not have been scoring any marks); this answer is attached.

I think that anyone would be doing very well to achieve this sort of answer in exam conditions; in terms of quantity I suspect that would equate to nearly 4 pages of typical handwriting which puts at the upper limit of what can reasonably be achieved in terms of quantity.  I think that this would "stake a good claim" to achieving the vast majority of the marks available; one can always further refine an answer but I'd like to think this would get in the high 90% if it had actually been produced in exam conditions. Therefore represents something to aspire to, rather than have a realistic chance of achieving in an exam; however it sets a benchmark for calibration-  i.e. if your answer could get some 50% of this content distributed evenly across the question, then it wouldn't be far off from achieving a Pass.



Question 8
Describe TWO distinct circumstances which might give an operational need for a train to enter a platform line already occupied by another train.                                                                                             [4marks]
For a signalling system of your choice, explain the following, giving reasons and identifying any limitations:

1. What action the signaller or automatic route setting system performs before initiating such an operational move.                                                                                                                              [4 marks]
   
2. What special interlocking conditions are proved before for this type of route can be set. [5 marks]
   
3. What information is given to the train driver and how is it conveyed.                         [4 marks]
   
4. What protection exists to prevent collision                                                                    [4 marks]
   
5. What additional measures could be provided to minimise risk of collision.                 [4 marks]
   

[Alan Beavers]

Thanks Peter, thank you for all your work over the weekend and else.
The move has to be scheduled otherwise the signaller has to talk to the driver, but where would this scheduling be - I know that TRUST gives platform nos. but what says whether it is permissive, is it the 'train running information' given to the signaller?
What else can be done on a shunt permissive move apart from an engine onto its train - empty coaching stock, what about ECS onto a loaded passenger already in the platform, can that be done?
Regards, Alan

[PJW]

Thanks Peter, thank you for all your work over the weekend and else.
The move has to be scheduled otherwise the signaller has to talk to the driver, but where would this scheduling be - I know that TRUST gives platform nos. but what says whether it is permissive, is it the 'train running information' given to the signaller?
What else can be done on a shunt permissive move apart from an engine onto its train - empty coaching stock, what about ECS onto a loaded passenger already in the platform, can that be done?
Regards, Alan

There are various sources of info to guide the signaller including the specific Signalbox Instructions and  Station Working books, but these are generic rather than looking at specific timetabled movements.
The Sectional Appendix would show which lines are defined as Permissive Passenger but not give any idea re which services can use it when.
I am not aware if nowadays such information is shown in the WTT Working Timetable.  It would be the logical place.  However I was always surprised how little detail was provided to signallers when a timetable changed. Seemed to be that they actually had to work out platform allocations for themselves in the few weeks prior the introduction of a new TT and create their own "platform simplifies" to work out which train should use which platform to minimise conflicts regarding arrival and departure times.  Thus it was often determined at a surprisingly local level, very close to implementation.  Presumably someone had worked out far earlier that things could work and perhaps the exercise was only supposed to be familiarising the local staff and transferring information into a form that was easier to use "real time" but it definitely was amended "them in ivory towers don't know really how to run a railway" taking into account local factors and knowledge based on years of experience about what could actually be expected rather than the theoretical scenario of the planner.  
I am out of touch with such things now, but I'd like to think that in the last 25years there is far more realism built into the timetable from the outset; far more data is available centrally via recording and logging, event replay etc. This is a long-winded way of saying: I don't really know but I think it is the WTT and where that doesn't specify then it is likely to be the relevant local operating manager who effectively signs off any locally developed station working information and also is responsible for issuing any specific local notices regarding regulation priorities or additional risk mitigation measures (often as a result of investigations into incidents) which the signallers are to implement.

As you say the intended platform allocations (however they are actually set) are included into a database accessible to the signallers (and indeed as a member of the public then you can get access to elements of this from websites selling rail tickets or Open Train Times etc.  Not sure if it is anywhere explicitly noted that it is a permissive move, but obviously this can be inferred if the move is timetabled when the platform is already occupied (well on the assumption there is no mid-platform signal of course).

I seem to remember that when considering the arrangements for Permissive Passenger and Permissive Freight operation (whose rules differ), that ECS is a bit of a "joker" in that it can be treated as either Passenger or Freight as convenient so therefore can mix with both, depending on the category of the other train.  Yes a shunt move can be used for joining an ECS multiple unit train onto another multiple unit train whether or not it has passengers in it, just as a loco can be signalled onto passsenger coaches.

[Alan Beavers]

Thanks Peter,

I think they still use 'simplifiers', I'm pretty sure the WTT doesn't specify permissive moves, but as you say it is obvious by use of the same platform.

[Jerry1237]

I may have misunderstood but surely Lime Street control is to manage permissive move[s]? On the Southern, when I live there, splitting and reforming was common- which equate to permissive moves. These must be inherent in the WTT. There are numerous places where freight can be stacked too.

Not sure signallers need to discuss permissive moves with a drivers. Driver's instructions are presented by aspect indications and route knowledge. PJW can correct me but a Y is a main route and suggests the route is clear to its exit. A sub would indicate a warner which would infer an occupied platform for an in service passenger train.

From memory, there is also an instruction for drivers to stop at a red lamp or short of any obstruction. This is one of the reasons buffer stops are not [rarely?] proved.

Reading about Lime Street control is actually an interesting feature to study and aid thinking for the exam..

Last point, if making statements about signaller requiring to speak to driver, quote that assumption in your answer. It may not comply with NR standards but then were should not using those in our answer anyhow but using first principles as the basis for our answer. Not all candidates will be from the UK or work on mainline!

Jerry

[PJW]

I may have misunderstood but surely Lime Street control is to manage permissive move[s]? On the Southern, when I live there, splitting and reforming was common- which equate to permissive moves. These must be inherent in the WTT. There are numerous places where freight can be stacked too.

Not sure signallers need to discuss permissive moves with a drivers. Driver's instructions are presented by aspect indications and route knowledge. PJW can correct me but a Y is a main route and suggests the route is clear to its exit. A sub would indicate a warner which would infer an occupied platform for an in service passenger train.

From memory, there is also an instruction for drivers to stop at a red lamp or short of any obstruction. This is one of the reasons buffer stops are not [rarely?] proved.

Reading about Lime Street control is actually an interesting feature to study and aid thinking for the exam..

Last point, if making statements about signaller requiring to speak to driver, quote that assumption in your answer. It may not comply with NR standards but then were should not using those in our answer anyhow but using first principles as the basis for our answer. Not all candidates will be from the UK or work on mainline!

Jerry

The issue is that Lime St control has nowadays more or less outlived its usefulness, with variable types of rolling stock, defensive driving policies etc.

Similarly nowadays unless it is regular timetabled move, signaller does tend to need to speak to driver (easier now anyway with GSM-R)- read the Plymouth accident report.