(18-09-2015, 07:14 PM)TheRailwaySignaller Wrote: The third [requirement] seems to me to be clearly hinting that signal 217 should have a restricted overlap so that crossover 1104 can remain in use with a train making a station stop. The same applies to the next operating requirement. It is strongly suggesting that there should be a ROL after 225.
On the up fast with the bi-directional signalling I notice that you have not placed track section joints to replace the signal. This is good as they are auto signals. However, the placement of overlaps could be improved. What is the purpose of section BAN? it adds extra joints without any operational benefit. The overlaps from 326 and 419 should be extended so that they share a joint. (I made the same mistake in my attempt at the 2013 paper and Peter pointed it out to me).
Other than S680, none of the signals have junction indicators. Some of the junction protecting signals are lacking any obvious form of junction signalling whilst others have been provided with standard indicators. Standard indicators are fine for lower speeds divergences such as the one into the terminal platform. The UK mainline standard is to use junction indicators for high speed turnouts. Furthermore, I would think that use of flashing yellows over the 100km/h divergences would be suitable.
Prior to connection between the goods line and the platform line trap points are needed for freight traffic.
All trap points should be provided with track circuit interrupters. (though in the case here, the TCs tend to end before the trap points, so not sure what should be done).
Generally, there shouldn't be staggered signals on parallel lines. The signals should be in line with each other which is not the case with 421 and 223. However, it is possible that this rule may be open for relaxation based on a risk assessment. Perhaps a note to show that you are aware of the rule would have been useful.
Some other points:
1) Signal S215 has a subsidiary signal incorrectly drawn with a stop aspect.
2)How come S215 to S214 is not MAR?
Hope this was useful, apologies for any inaccuracies, im in a learner myself!
Agreed,
- 217 does require a ROL so that 415 can be routed from platform 2 to the Down Slow whilst another train enters the platform 3 from the Branch
- 225 does need a ROL so that a train can be signalled into station G platform with points 1101 Normal for a train to pass on the Down Main
- It is a common mistake that students place a signal and simply measure 180m and mark an obverlap joint wherever that falls without really thinking. Yes a longer overlap does affect headways, but actually very little effect - typically a few seconds unless the speed is very low. Even worse than superflous sections (more money to provide,more cost to maintain less reliability) are overlaps that are 180m from signal that fall in silly places within pointwork (e.g. places that are physically impossible, places that are foul unnecessarily etc.) In fact you should actually think of the various possible places a track joint would be possible and which ones might be a potentially sensible position for an overlap BEFORE finalising the position of a junction protecting signal. I also noticed that there are several signals provided with overlaps incorrectly as they mean nothing ifthe signal cannot be approached (and indeed are not generally provided unless there is a main aspect signalled move up to the signal).
- The IRSE examiners do not put information in a question (and that includes notes etc. on the module 2 layout) without reason; the signalling provided should be appropriate for the junction divergence speeds and yes in this case for UK signalling the junction signal must have a PLJI, MAY-FA approach release and the relevant flashing aspect sequence on approach.
- Definitely need traps to protect passenger railway from freight lines, siding and any loops (BOTH ends thereof) where unattended vehicles may be left- in this case the connection is "end-on" but yes trap points are needed. Indeed none of the trap points that have been included are drawn well- it should be clear in which direction they derail and the track circuit interrupter clearly attached to the running edge of the stock rail with a clear gap from the curved stock rail that should look just like a normal point does and indeed be numbered!
The thing that is wrong is that the track circuits end before the trap points! For example in the case of station E Up Siding, the end of track circuiting symbol should be just to the left of 501 GPL so that a train passing the signal is immediately being detected and, should the 1106B points not be Reverse, the train wheels then destroy the Track Circuit Interrupter prior to becoming derailed so that the track cannot become clear again even if no longer shunted.
- Certainly signals should not be staggered unless there is a rational reason! Not only is there sometimes a risk associated with driver misreading, particularly on curves when the relative position of staggered signals may appear to alter as they are approached, ut just from practical grounds re placing location cases etc. there are disadvantages. So it is ridiculous that signals such as 219 and 417, neither of whose placement seems in any sense critically constrained are 90m apart. Conversely signal 205 clearly has to be positioned at the end of the platform at station B and it is important that the overlap of signal 203 must permit the use of 1109 points reverse, so that stagger is inevitable and given the geography and likely speed, there really is no significant risk associated anyway - hence that is perfectly acceptable.
1. Some of the numbered list of notes provided probably weren't worth writing as they do not really affect the how the layout was signalled. It does not matter whether the points are operated by HW point machines- the only thing to make clear is if any points are exceptions in that they are
a) operated by immediately adjacent hand levers, or
b) from a Ground Frame facility in the vicinity
and you can do this by symbols.
Similarly other than placing constraints on signal structures and provoking unwanted questions re where any neutral sections are located, specifying that the area is ac electrified really is not significant.
Again by specifying that dc (ac immune) track circuits are provided, all that provokes in my mind is why then you have drawn track section lengths quite a bit longer than could be made to work! Rather than giving you any marks for specifying, I would be more likely to deduct marks, whereas if you hadn't stated then I'd be reasonably comfortable that track sections might be ok up to around 1000m.
I think notes 4 & 5 were worth making, and I'd also have add that TPWS provided at junction protecting signals.
However note 6 doesn't really add anything; indeed given that several trap points are not numbered at all and also rather inconsistent numbering of 1107/1108, if I were an examiner I wouldn't be convinced the student actually understood the note and might assume that they had just regurgitated.
Another area where "less is more" would be the marking of the Clearance Points. The problem is that the vast majority of CPs are marked in places which just would not be clear. Where tracks are spaced at a nominal 6ft (as one might well assume adjacent tracks would be unless there is any particular evidence to the contrary) then the CP for a crossover would be approximately opposite the switch tips. I'd be prepared to accept the CPs drawn at 1104 and at 1105 and perhaps 1108 as actually being feasible; the Branch is clearly a fair distance from the Down Main given the island platform 2&3 (similarly the CP for 1110 and the CP for 1101 where the depiction does indeed suggest a relatively wide separation) but all the others scream WRONG.
I would not mark the obvious CPs at all; just those that are looking marginal and you want to emphasize to the examiner that you consider a particular joint to be clear- however you lose all credibility if you mark things as clear which patently are not.
In a similar vein, you have placed some signal structures between the Down Fast and the Up Main; there wouldn't be space between the tracks to place them like that. You could have drawn then cantilevered from the cess had you not defined this as ac electrified railway, but since you have then you'd basically need to draw gantries spanning all tracks and the signal heads hanging downwards from it. Given the wider than nominal spacing of the Down Slow and Down Fast, then I am prepared to believe that signals such as 417 would be possible.
The Branch is quite oversignalled; the calculations suggest that a maximum of 2 block sections needed in each direction. So 314 at station C would only be a Red/Green and 312 only a Yellow/Green distant for 310 (which actually would be far better positioned at least 300m towards station B). Signal 316 would just be a Yellow/Green and, if you need it at all, signal 318 would be a Red/Green.
In the other direction, signal 215 would be better placed some 200m closer to station E and a Yellow /Green signal at just about minimum braking distance would be deployed instead of signal 213. Signal 211 at station C would just be a Red/Green and similarly would have a Yellow/Green on the approach in lieu of signal 209. Signal 207 would not be provided.
It was the area approaching the Freight Depot which was the most adrift.
- Certainly can't have an auto signal 308 reading over points 1111 and having 1112 in the overlap beyond 306; it also should not have a Green since 306 is a fixed Red with a PL
- It is not clear where the boundary between the area of control of the main signalbox and whatever controls the Freight Depot actually is; indeed can't even tell which bits of railway are track circuited and which are not
- Signal 506 seems potentially superfluous and appears not to have any train detection, reads through a set of gates blocking the railway but appears to have a route indicator presumably selected on the lie of a set of handpoints that do not seem to be electrically detected- so it looks a mess!
- If we envisage a freight train hauled to 306, the locomotive then uncoupled from its train and then signalled via 306's PL whilst its wagons are left on the running line, we then have a PL on 201 to signal it into the Run-round line, so this is all good so far. The loco can then run ll the way into the neck and be signalled back onto its train using 505; I'd have expected it to the left of the line, but I suppose if the driver is actually permitted to get back onto the train driving from the furthest cab (but see later!) I suppose it could make sense to have this between the tracks (but still does not excuse the signal being drawn on its side!). Certainly the runround move is possible (but there is no way of signalling in/ out of the little siding should there be a need to leave a vehicle there and therefore this area incomplete) and the train is ready to be propelled into the depot.
- If the driver is in the cab from which he could have seen 505 as drawn, then not going to be able to see 306 PL- it's 400m away and on the other side of the line with the train blocking any visibility. Need to think carefully about how this area would be operated and then add some notes to explain whilst making sire that the signalling shown on the plan is compatible. Propelling a long freight train always has its risks; when the signals are GPLs and there is a set of gates that need to be opened from being across the line and handpoints involved,if not careful it is an accident waiting to happen!
- Similar considerations apply to train leaving the depot; what controls would actually be in those GPLs at end of yard sidings, who controls them etc?
Actually I think that rather less controlled signalling here is the answer; 1111 and 1112 should be operated by train crew via a Ground Frame, perhaps released by train staff and many of the movements being authorised by the guard trackside at one extremity of the train via a back-back radio to the driver at the other.
So there is quite a lot that could have been better in many respects on this layout; however I have actually seen quite a bit worse and it is substantially complete. There are some things that particularly detract:
- CPs
- Overlaps
- Route Indicators
- Trap points and TCIs
- Signals on wrong side of line / between tracks where couldn't fit
PJW