2011 mod2 layout

[Nagasri.Jonna]

Hi PJW,
We are attaching solved 2011 layout for module 2.Please find and we got some doubts while solving the layout:
1. when we calculate headway for branch line between A&D, we got 2 aspect signalling. For C to F, we got 4 aspect signalling.
Kindly suggest, how to make trasition between 2 and 4 aspect signalling or can we show 4-aspect for all lines as we followed in yard.
2. What are the considerations, when there is head shunt or run round lines in the yard?


Regards,
Nagasri.J

[PJW]

I'll need to defer feedback on the calcs and layout until I have more time, but yes you will find that different areas will have different requirements.

Generically if you have a line signalled with 2 aspect signals (isolated 3 aspect signalling) diverging from a 4 aspect signalled line then the junction signal for the diverging route may be arranged to show just red or green which authorises to train to travel a considerable distance, passing a single yellow distant to a red at the first stop signal.

In the opposite direction, the junction signal from the branch authorising movement onto the 4 aspect line at the convergence would most likely be a three aspect signal as the speeds are probably such that when displaying a single yellow that there would be full braking distance at the junction speed to be able to stop at the first 4-aspect displaying red. The branch would have a yellow/green distant signal (plated with s delta plate) on the approach to this 3-aspect.
Otherwise if the first 4-aspect beyond the convergence isn't sufficiently far from the junction protecting signal for the attainable speed, then the junction protecting signal on the branch would need to be a 4-aspect in which case its distant would be a 3 aspect head but a yellow/green/yellow (and plated with a delta plate).

I'll respond in more detail when I have had a chance to look at your attempt; I have written this without having looked at all and just on the basis of the text of your post so hopefully I have understood your query correctly.

Similarly item2 will have to wait until I can look.

Hi PJW,
We are attaching solved 2011 layout for module 2.Please find and we got some doubts while solving the layout:
1. when we calculate headway for branch line between A&D, we got 2 aspect signalling. For C to F, we got 4 aspect signalling.
Kindly suggest, how to make transition between 2 and 4 aspect signalling or can we show 4-aspect for all lines as we followed in yard.
2. What are the considerations, when there is head shunt or run round lines in the yard?


Regards,
Nagasri.J

[PJW]

Feedback on the calcs now given in separate thread ; further feedback on the layout will have to wait until tomorrow evening- however to answer your specific queries now....

1. First thing to point out is that as well as the low level of freight and the hourly stopping passenger, the line A to F must also be able to take the 2 per hour fast passenger trains which usually travel between C & F but are sometimes diverted via A instead. Did you factor that in to your consideration? [I did not see anything recorded in your calculations about this area of railway= why not?]
I guess so as even if we make the perhaps excessive assumption that the two 3 hourly freights happen to occur in the same hour, this still only makes 5 trains per hour and the headway specified is 10 minutes so there is still a spare train path even with the diversions.
At 25m/s then we only need a Red/ Green section signal every 15km approx with a Yellow / Green at braking distance some 775m on the approach to each; clearly isolated 3 aspect signalling is what is needed from a headway perspective.
I note though that you have placed 4 aspects here; that was not the thing to have done!

However probably not a good idea to have a very long section just beyond station D as that could result in late or slow running on the branch impacting the mainline. We do not need to keep the block sections of the same length and hence I'd be tempted to place a stop signal protecting the tunnel at B (far enough outside that the end of its overlap track circuit is still in the open air) and place its distant accordingly; this has the added bonus of having a signal at the tunnel to improve both safety and operability. Given that in the other direction there could be a need to hold a train on the branch prior to the station / yard, then another signal on the Down Branch just outside the far end of the tunnel would also bring twin benefits.

So there is clear rationale just thinking about the traffic pattern, but the thing which makes this absolutely essential are those few words written under the depiction of the tunnel on the layout plan. "Limited clearance- trains not permitted to pass in tunnel". This means that the tunnel is too narrow for a train on one track safely to pass one on the other. Perhaps they may not hit, but there ould not be enough passing clearance and the forces due to the wind effect of two trains travelling at speed in a narrow bore tunnel could potentially cause deailment. Therefore the length of the tunnel has to be signalled almost as if it were a single line section; only one train allowed in the tunnel at any one time; therefore signals as close as practicable to the tunnel entrances are essential. This is a case where I would provide the signals with a route bocx despite only having one route each, so that I could explain the need to interlocking them against each other.

I'd then be showing the next signals for the two directions of travel on that Not to Scale piece of the layout beyond the Zero point at "A", drawing the section signal and distant for each line, remembering to show the dimensions relative to those signals on the main body of the plan I have just described. This railway may well be sensible to equip with axle counters, seeing as the sections are long and would be a more economical solution avoiding multiple track sections and associated locations and power- indeed if the tunnel is a wet one there would also be another benefit.


2. I note that you have put a lot of signalling in the yard; given the level of traffic that was probably rather extravagant. Indeed if you read the notes it does tell you that at yard E the interface between signalled movements and yard working must be shown; there is therefore a very clear inference that the examiners are not expecting the whole area to be signalled as then there would be no interface!

Look also at the other notes on the left end of the plan where it tells you to provide full signalling for the runaround movements- further evidence that don't expect full signalling everywhere. Also read what moves are needed- how freight can enter / leave and the means of run-round.

Trains from C will have a loco on the right hand end and need to enter yard via Down Main platform, then opull forward into headshunt, then loco push wagons back into siding before uncoupling, possibly to go to loco spur. trains from A similarly except they have choice whether to enter via the runaround (probably the preferential route on most occasions).

When a train has to be prepared to leave then the loco must fetch the wagons and pull from siding into headshunt, before propelling back into the run round line. Loco then detaches, moves into the Arrival / Departure line before shunting through the platform koving contrary to normal traffic along the Down Main until it has cleared what you have numbered 312B points and then rejoins its train in the run round. If it is destined for A then the whole train can then leave , passing over 312B and 311B/A. If however it is destined for C then the loco must propelling it train back again into the Arrival / Departure line before exiting via the Down Main platform and then via the crossover you have called 315A/B.
That is what you are supposed to have provided the appropriate signalling to achieve; now that you understand this you may care to make some modifications to your plan!

Perhaps it would be a good idea when doing this also to consider where you need trap points to protect the running lines from places where vehicles can be left unattended, in sidings and goods loops etc as there seem to be some missing......


I will have a few more comments when I have longer to respond, but certainly in general you seem to have got the right idea. Careful about the orientation of the GPL symbols though; the edge of the symbol closest to the track should be drawn parallel to it and the curved portion on the furthest side away from 9 o'clock to 12 o'clock when seen from the driver's position- also from this orientation there should be the two dots which nowadays are joined with a "horizontal" bar, the 3rd dot should form a 45 degree line with that at the righthand end of the bar.



.

Hi PJW,
We are attaching solved 2011 layout for module 2.Please find and we got some doubts while solving the layout:
1. when we calculate headway for branch line between A&D, we got 2 aspect signalling. For C to F, we got 4 aspect signalling.
Kindly suggest, how to make transition between 2 and 4 aspect signalling or can we show 4-aspect for all lines as we followed in yard.

2. What are the considerations, when there is head shunt or run round lines in the yard?


Regards,
Nagasri.J

[/quote]

[reuben]

Apologies, Peter has in his usual attentive way beaten me to to it, but I have some more detailed comments on the yard area.

At a quick glance this looks like a good solution which should score well in the exam (if you have time to complete the layout to this level of detail)

Regarding the yard arrangements:

I have provided a scan of a quick sketch of my alternative arrangement.

1. You have rather over-signalled the headshunt/ sidings area. This isn’t technically wrong, but an example of over-provision, just like providing 4 aspect signalling where 2 aspect would suffice. The usual “UK mainline” practice for the operation of non-passenger yard areas is to be unsignalled – no track circuits, signals or powered points. All movements are directed by a person in charge “shunter”, who physically checks conditions are safe before giving verbal authorities. This is considered reasonably safe, given the very low speed of such movements and lack of passengers. There does need to be a clear demarcation between the signaller-controlled and shunter-controlled areas.The “stop await instructions” notice at the end of the A&D line is the end of the signaller-controlled area, from which point the shunter gives a verbal authority. Shunt signal 906 is the opposite interface. The other notice boards are “virtual signals” used by the shunter to regulate movements.

2 In order for a train to enter any area on a main class route (authorised with at least Y aspect, there must be train detection all through the route, a "main" exit signal and overlap or energy absorbing buffer stop. Given the requirement in the spec for signalled run-round movements, entry into the run round and A&D lines from the running lines must be on signalled routes, but equally easily on Main or Shunt class. I have chosen to provide a main class route from 1007 to 1009 (fixed red signal to terminate main class route) , but shunt class routes from 1009 and 211 to the notice board, which can serve as a shunt class route exit “signal”.

3 notice how signals 1008, 904 and the notice board have been placed clear of the pointwork, so that a train can approach any of these whilst the points are in use by other moves.

4. The required run-round moves via the down main take place via 1009, 904, 210 and 901 signals. In case there is a need to get the loco back afterwards, I’ve given 901 an additional route to 211 and to 1008, but the rest of the move via 211 and 904 uses routes which must be provided anyway. I chose to position limit of shunt 900 and its overlap to the right of 1007, so that moves to 900 do not restrict moves up to 1007 – this does make 901 a preset shunt signal, however.

5. To enable the freight trains to depart without delay, I have provided main signals 1008 and 210. 1008 only needs to be R/G because the next 2 aspect stop signal has its own distant, whereas 210 also has a route to 204, so it also needs a Y - see Peter’s explanation about no need for YY. As there’s no “fastest” route, a standard indicator is used for both main routes. 210 also needs a subsidiary and miniature route indicator for the shunt class route to LOS 900.

6. Wherever non-passenger lines interface with passenger lines there must be trap points to protect the passengers. Although the spec doesn’t say if the Run Round line is “passenger” or not, there is no need for passenger trains to use it and, crucially, the freight vehicles must be left “unattended” whilst the loco runs round. Therefore, trap poinst must be provided to protect passenger trains against a run-away freight vehicle. Points 418 naturally perform the trapping function at one interface (or strictly 417 whilst a loco enters or leaves the loco spur). However, additional trap points 412B are needed a the other interface as there are no naturally occurring point to use here.

7. Because of the restriction upon trains passing in the tunnel, this places an additional “headway” constraint. To minimise the conflict between up and down trains here, signals 1003 and 1002 are positioned with overlaps clear of the tunnel. They are not “protecting signals”, but instead to positioned to delay until as late as possible the time at which an approaching train needs a route to be set through the tunnel. 1003 and 1002 need to both be normally at red, and could either be signaller-controlled or “automatically selected” on a first-come, first-served basis.

Reuben

[PJW]

Great- a picture is worth a thousand words!

Consider though that I'd probably have made 904 to have a main aspect for routing a departing train up to 210, but I agree not 100% essential dependent upon utilisatio. Also could have some benefit for a train propelling from the headshunt as rather more visible from a distance to assist the driver stop prior to it when their driving cab is a very long way away (but probably move may be assisted by shunter / guard in continuous radio contact with driver).

Apologies, Peter has in his usual attentive way beaten me to to it, but I have some more detailed comments on the yard area.

Reuben

[PJW]

You correctly declared the railway's practice used for the plan.

It would have been better to have used the word "Notes" rather than "Assumptions" above your numbered items.
1. Suggest reword to: "AWS fitted to all running signals at 180m. Suppressors provided on bi-directional lines".
2. OK.
3. Suggest delete; this note makes no sense. A crossover between opposite direction running lines consists of a pair of facing points or alternatively a pair of trailing points, but you aren't going to call the two ends both A in the first case and both B in the second case!
4. You mean "electrically" rather than "electronically". Note sure really need this note (and if you follow Reuben's and my advice then you'd actually have some handpoints so it wouldn't be true.
5. You meant this to apply just to 4 aspects on the Main line; actually not sure really needed as you covered this in your calculation write up.

A few other things:
a) You have an overlap beyond the station D Down main platform starter (doesn't seem to be numbered) into the sidings. Suggest shouldn't be shown, or at least qualified with a note "only valid when forward route set",
b) You have drawn a ROL beyond 206 signal, but in this case this gives no advantage. One provides a ROL when it gives additional layout flexibility by not locking TRAILING points (which can then be used to route a different train). The full overlap that you have drawn on the Up Main is FOUL of 313 Reverse; you should have placed it further away so that it was clear, it would be a bit over 180m but that wouldn't be a problem- indeed you have placed the alternative leg of the swinging overlap sensibly at 240m
c) Given the signalling that you have provided in the Yard, you forgot that you needed a signal on the Arrival & Departure to protect 320 points, parallel to 239. at the AN / AO joint. This ought to be a main aspect Red with an associated PL for pulling ahead into the headshunt.
d) Similarly you'd need a similar signal protecting points 319 on the Run Round, opposite signal 209. Again there is a protecting signal missing at the other end of the Run Round protecting 312B at the AJ /AK joint. You probably would then not need signal 108.
e) 206 route box. Why doesn't the A route show Y/YY/G?
The PLJI for the B route is actually pos 4.

Although Reuben and I have between us pointed out quite a few things to learn from and the thread is not exhaustive, actually the overall impression is pretty reasonable. If you make sure that you don't throw marks away by missing trap points or signals protecting conflicts etc and make sure that you really read and understand the operational notes on the plan and provide the signalling to enable the operational moves, then I think you'll probably pass provided that you are fast enough to get a significant proportion of the layout broadly completed in the time available.

[dorothy.pipet]

Blank 2011 layout fyi