2000 Headway Calcs and Layout

[PJW]

(19-07-2010 10:56 PM)interesting_signal Wrote:  Comments would particularly be welcome on the single lines section as I'm a bit unsure on that, in particular when the train comes out of the single line section. I'm not sure that signal 132 is correct. Do I need another signal before the junction in order to warn the driver that signal 132 is at red. Not sure what driver's expectation is when they come to the end of the single line section.

Regarding the single line, as you suspected you haven

[PJW]

(19-07-2010 10:56 PM)interesting_signal Wrote:  Another issue I'm unsure of is the shunting/reversing of passenger trains. Should my signal 1004 be a main signal (for the purpose of shunting/reversing passenger trains) or is a PL acceptable? Then would 1003 LOS need to be a fixed red too?

To modern standards any signal that authorises a right-away running aspect for a train should be a main signal; in the past the railway economised by only providing a GPL (or exceptionally an elevated PL) as the exit signal from goods sidings if there was not a large number of train movements (e.g. typically under a dozen per week).

Your question particularly asked re provision of routes for the moving of passenger trains around the layout. Where a main running move exists to route the train in the right direction, then this suffices and no specific shunting route is provided; i.e. there is no need nowadays to provide a PL aspect on a platform starter to inform the driver that they are required to travel only sufficient distance to clear a set of points and get behind a GPL in order to be routed back towards the station into a different platform. The driver is expected to know the move they are going to make and not continue as far as the main route actually gives authority; this is a change from earlier times when there was far less possibility of verbal communication between driver and signaller and hence specific signals were provided so that there was no possible ambiguity re the intended move.
If however there is a need for such a movement to be made where there is no such running move already provided, then the route is provided as a shunt route and therefore display a PL aspect. In many cases therefore, such routes are provided along a running line in the opposite direction for which it is signalled and therefore will be limited by a LOS. Do remember that wherever there is a LOS there will be a move up to it and that this constitutes an opposing move conflicting with the normal running moves along that line; hence any such signal must be a controlled signal rather than an Automatic.

Your specific query related to signal 1004- to be honest I can't see that number but assume that it must be the one at the other end of the Up Platform at station D to 128. A GPL is exactly what you should have here and similarly 1003 is also correct as a LOS. Providing as main signals would just be more expensive and potentially give more potential miseading problems to confuse drivers on the Down Main. Hence you got this correct.

[PJW]

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[quote='PJW' pid='1783' dateline='1279610386']
The scan of the layout only appears to be the central portion showing junctions C and E; perhaps you may need to scan the long layout in several separate files. Hence I don

[PJW]

(19-07-2010 10:56 PM)interesting_signal Wrote:  It's taken me a while to get back to this but I've finished my attempt at signalling this layout.
Any comments would be appreciated.

Well done for reading the instructions and permitting a train from the branch to be terminated in either the Bay or the Down Main platform and then reverse. Actually 132 needs relevant route indicator for main route to achieve this but let's assume that this omission was a careless slip.

Arguable whether really need traps 601B, but certainly not wrong- historically bays often had traps because newpaper and parcels vans were often left at the buffer stop ends, but those days have passed and therefore not generally now provided. The Up siding certainly needs them. Just be careful to make obvious that the TCI is on the spur rail deflecting into the cess, not the running rail- due to resolution, I can't be sure what you have drawn.

I don't see the advantage of the ROL between EG and EH; there isn't room for a ROL beyond 127 prior to 601 points that might have been useful, but since you need to lock 601N there is no route possible that would not have been possible with the full overlap over 603. Therefore do not provide.

I am assuming that EH/EJ joint is denoting an overlap beyond 132 adjoinng one beyond 127; reasonably clear but may have been worth a note.

Not yet studed route boxes but don't see why two route indicators associated with PL for 127 and 129. Also since the parallel GPLs also read to the LOS, even though they only have one route I'd have given an "X" route indication as well.

136 should NOT be an Auto because of the moves to the LOS which oppose it; should be a controlled signal with an Auto working facility. You were right to have a track joint beyond the LOS so that any overrun becomes obvious to the signaller- remember that there is no TPWS and that by theri nature there can be a long lengt of train being propelled in front of the locomotive (whereas multiple unit trains would be driven from the cab at that end and then the driver change ends, perhaps by walking through the train, and indeed trains in the Down diretion may be pulled across the facing crossover before then being set back into the Up sSiding, there is always the possibility that one of the freight trains which are to reverse at D may need to make such a move on an odd occasion.

The fixed red 130 is just what is required there; however you have not marked its overlap and I also believe that it should have a joint close to it so that signaller would know if SPADed.
However on the scan I can't see where EE ends and AJ ends so perhaps I am missing something. In fact the AH/AJ joint could well have been the overlap joint beyond 130 as well as for 125- who cares if 130's overlap is 500m long?- it is no disadvantage and don't spend money needlessly.

The question I have though is:
how do you envisage that the freight that runs from A to B is to operate?
From the Down platform I see you have a route for the loco to the LOS on the Up, then normal signals on the Up to junction C in order to get behind 1001 (even though it is further from 505 than it need be) and then back along the Down, but
a) what happens when the loco gets to 125? T
his will be at red because track EE will be occupied by the wagons of the freight train,
b) what would you then do (assuming that you get the loco onto the lefthand end of the train); how does that train proceed to junction C?

I am guessing that you envisage setting back onto the Up Main again and then running under the normal signalling. This is OK but you should really have put a brief note to describe operation.
Did you consider giving 130 a main aspect and providing reversible signalling up to junction C along the Down?
I think perhaps you did because that would seem to be the role of 122 to regain the correct line.

Something isn't tying together; I think that you can see that if you had expllained a bit more then I would be able to give you that much more credit as I could recognise your intention, despite what might be a bit of a silly slip oversight in execution.

[interesting_signal]

(20-07-2010 10:29 PM)PJW Wrote:  The question I have though is:
how do you envisage that the freight that runs from A to B is to operate?

I'm still digesting some of the comments, but I'll answer the last question first.

For the freight train my intention was that the train from A comes onto the Down Main and leaves the wagons here, behind signal 123 (at night so ok to leave on the main line/saves the energy wasted in having to haul them all the way to the station only to come back again). The loco continues to station D, and then up to 1003 LOS, reverses and continues on the main line via 134 all the way up to 120 so that it's behind 1001. From 1001 shunts up to the wagons/behind 122. Then from 122 goes back onto the Up main and continues to B.

[PJW]

As said before, in general ok and a good minimalistic presentation for the exam- probably worth though having another column for main aspect / PL.

1. I believe you should have put Auto Facility on mre troutes; 127A9M), 134B(M) for e.g. but this is minor.

2. You have provided some shunt routes for no obvious reason such as 127A(S) where there is 127A(M)- see earlier post in thread re provision of shunt moves and running moves. Ironically the one that would have been useful was the one you didn't provide: 125A(S)- see the post re operation of station D and the inability to signal the loco back onto its freight train after the runaround move.

3. When having a route to a LOS, then the generally accepted indication is "X" to denote a "wrong direction" move- particularly if propelling a train, a driver has to be particularly careful not to overrun a ground mounted signal and needs specifically to be on the look out for it rather than looking high for a main running signal and this "X" is supposed to be a reminder of that.

4. I think you must be a bit confused re route classes in the UK- perhaps there is a bit of Australian practice to get out of your system....
A (S) class route is for shunting; not for use by a passenger train (except possibly as Empty Coaching Stock when not in public service). Signals 132 and 134 definitely need Main class routes into the relevant platforms including the bay platform. You might also choose to provide Call-on class routes (which display a PL but are distinct from shunt routes) to authorise a passenger train into an occupied platform where such a method of working is necessary and justified.
There is nothing in the station working that demands such (e.g. the joining of separate trains) nor is there any hint that there needs to be platform sharing by different trains to achieve the train service defined. Probably worth an assumption statement one way or the other; in this case it seems that the platforms are only as long as the passenger train length so to me that would be the final piece of evidence I'd use to say ASSUME NOT.
However had there been some reference to the stopping passengers only being 100m, then could well have said that providing call-ons into the bay would permit a service from G to F and also one from F to G both to be accommodated there for a short while, clear of the Down Main to let an express through before departing in quick succession to take the opposite directions at junction E. In such a scenario could be really useful to provide that facility even if rarely used (i.e. when all trains running to timetable not needed but invaluable to minimise effect of service perturbations); obviously in this case since two trains won't both fit then the idea would be a non-starter.

125A(W) isn't needed (see earlier post in thread re the ROL provided being of no value in this case)

Overall though these route boxes themselves were fine- it was just that they revealed a bit of weakness of your understanding which hopefully the above should help strengthen.

[PJW]

127 and 129 need to be platform starters and given the braking distance constraints then 131 falls wher it does which is fine, but I think that I'd have opened up the spacing to put 133 further away (to meet headway and overbraking but be more economical) and also indicated a further signal (not to scale) at the interface at F [generally plans nowadays show a specific NTS little portion- if so then use it to show the next signa and dimension it, I think it is good to show this owned by adjacent signalbox].

I'd have attempted to place 125 closer to the station (whilst honouring reasonably equal spacing, it is sensible to use the flexibility of 4 aspects to engineer a slightly shorter section on the approach to a staion where trains stop to counterbalance this a bit to mimimise headway impact. Also since we need a PL here and a long slow move to get the loco back on the freight train if we can make this say 800m rather than 1000m (and obviously compensate by the section behind being a bit over 1000m to be able to get minimum braking) then that is another gain.

Certainly a good idea that 123 is sufficiently beyond junction that a 400m long freight train held at it doesn't foul junction C- when you have thought of things like this, then worth while annotating plan showing a line backwads from the signal to show that you know you have achieved standage, rather than let th examiner guess whetheer or not that was a fluke!

121 is quite a bit away from the junction; if it could have gone a bit closer then that would have been good- however if not then it is ok where it is. As befoe I'd have shown in the NTS area at B the signal in rear, again at the biggest acceptable spacing.

I think I'd have put 101 closer to the junction. Parallelism with 121 isn't an issue as the line is almost certaily coming in at an angle and there would be no intervisibility and not on the same formation- recognise that the plan depiction is purely diagramatic in this regard. Braking isn't an issue as the speed restriction over 503R is only 40km/h. Hence 'd have decided upon the length of the overlap suitable (calculated TPWS effectiveness for a freight train to have a good chance of stopping prir to derailing at traps) ad then worked back t o place the signal which I'd habve made 3 aspect. Since we only have one train an hour and the line speed is 100km/h I certainly don't need a section signal in rear very close, so I would have put a Yellow/Green at (freight @ 100km/h) braking distance back and then at the NTS portion near "A" have indicated the position of the Red/Green as being "where required to protect any infrastructure hazard but perhaps 25km away"

I wonder which signal you placed first in the oposite direction. You have 128/130 at the platform ends which are fine, but they don't actually need to be there, so these would not have been constraints.

Junction C is more of the issue; you have 124 in a good place, however there are options such as putting it closer such that its overlap fallsbetween 505B & 504 (since 505 only used by the runaround freight by night then locking them in overlap is hardly a disadvantage) or even closer and have an overlap oint between DH & DG [funny- it looks like one on your plan- perhaps you investigated such an option....]. The reason for moving it would be if it gave advantage elsewhere.
My motivation is that I feel 134 is toofar from station D, given the regular stopping trains that need to crossto the Down side platforms to reverse. Approach releasing 134 and then continuing for a long way before reaching the first se of points across which to diverge isn't good signalling; I'd like to get 134 much more into the area of 132 and then place them exactly parallel. If the cost of doing that is to slightly complicate the locking (note that with swinging overlap it is not in the slightest operationally restrictive) at junction C then that is a small price to pay. Moving 128/130 off the platform ends by at least 200m so their AWS falls outside the platform is actually a good thing- gets rid of 128 as a platform starter and the associated SASSPAD risk.

Whereever I ended up placing 124 then I'd place 122 opposite it (but made a 3-aspect provided I'd satisfied myself re attainable speed at 120 for waring of the next red). I'd then put a Yellow/Green distant for 122 at suitable braking distance and change 130 to be a Red /Green and hence made this part of the line reversibly signalled for that night freight movement to avoid that propoelling move to LOS on the Up Main on the grounds of a) improved safety, b) considerable time saving and put a note to taht effect to justify my decision.

Otherwise similar comments re placing signals at fringes and I would have shown isolated 3 aspect (stop and distant) on the freight line and probably 3 aspects spaced a bare minimum braking on the line to B (which after all was what the calculations suggested would be possible in a plain line section)

[PJW]

(21-07-2010 10:34 PM)interesting_signal Wrote:  

(20-07-2010 10:29 PM)PJW Wrote:  The question I have though is:
how do you envisage that the freight that runs from A to B is to operate?

I'm still digesting some of the comments, but I'll answer the last question first.

For the freight train my intention was that the train from A comes onto the Down Main and leaves the wagons here, behind signal 123 (at night so ok to leave on the main line/saves the energy wasted in having to haul them all the way to the station only to come back again). The loco continues to station D, and then up to 1003 LOS, reverses and continues on the main line via 134 all the way up to 120 so that it's behind 1001. From 1001 shunts up to the wagons/behind 122. Then from 122 goes back onto the Up main and continues to B.

Excellent solution; I agree that it saves energy, time and signalling.
However do you see how easy for the examiner to fail to see that, because you gave no hint of your intention?
Agreed the signalling to do that was there, but there were also a few hints that seemed to contradict. Positioning of LOS seemed to allow a whole freight train to be propelled behind 134, not just to accomodate a light loco or a multiple unit; whereas it might certainly be useful to have the ability to do this in extremis (e.g. taking a defective wagon out of the centre of the train and setting back into the siding for rectification later), because you didn't explain it seemed to suggest that this was the route the freight would nomally take and hence influences the examiners' assumption of your intentions. Then taking into account the facts that
a) you provided some (S) class routes on the layout that were not needed / inappropriate (see Route Tables) adds to the general feelling that you were rather hazy in this area.
b) The signalling of the junction E with a signal missing and 132 without a distant makes it possible that 122 is in same category.
Hence rightly or wrongly the various other defects of your layout are taken into consideration when trying to establish what might have been going through your mind in this instance.....

So I judged you unfairly and would have marked you down incorrectly. The examiners do not have this opportunity for dialogue to probe your understanding and can only judge on what is actually presented. A brief note on the plan re the operation would have made all the difference (to be fair I can see a note near 123, but on my print out at least I can't quite read so the penny didn't drop. It does include the word standage so perhaps this is it and I apologise).

Actually overall the plan was really very good for a first real attempt I can see that you have considered the various trains listed in contracted paths (even though again I have difficulty (resolution of scan, faint, print size and my eyesight) exactly what you have written. You didn't really address the "Methods of Working" sufficiently though-
you show the OTW-NS on the Branch but could have put a sentence of explanation,
didn't declare TCB on the rest of the layout
should have added a few words re assumption whether permissive wotking in the station needed, any assumption re the move to the LOS / use of the Up siding and the operation of the night freight would have rounded things off and potentially saved being misinterpreted.