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So basically, keep the main aspects that I have at either end of the Down valley branch but lose the sub signals at Station C and the main aspect at 1780m?
nthomso3 Wrote:Surely you could put just a IPL at 1300m and use it as a preset shunt for main routes along the DOWN VALLEY BRANCH?

There should be no shunt moves up to such a signal over the viaduct and therefore nothing will stop at it!


Indeed. probert1 has correctly explained the options for getting stock from the DM platform into the siding. I think that I's put a GPL at 1300 as suggested by nthomso3 which would be a pre-set shunt as described. Indeed probably also another one at 1750 protecting the crossovertowards the branch and sidings- this is also useful for train from UM platform to reverse. Obviously if you did decide to place a main running signal just a little way onto the viaduct then it would be given a PL aspect to read up to the GPL at 1750; this rather pre-supposes that the driver can walk through the rolling stock from one cab to the other without descending to ballast level.

nthomso3 is quite right- there would be ne shunt move up to the GPL at 1300; it would either be used for a train to change direction or would be pre-set by the main signal in rear and thus no moving train would ever encounter it at red.

PJW
Astubbs Wrote:The spec specifies standage in both directions on the DVB. I interpret it in this case as meaning the freight will be held to allow fast passenger trains to proceed on the mainline in both directions, and also allowing trains joining the branch from the up main to overtake. Once the coast is clear the freight can proceed. Standage isnt only made available for trains shunting.

I believe you need main signals at both ends of the down valley branch as it mearly forms part of the freights main class route (B-C).

i doubt you would ever allow a train to proceed from an IPL some 700m over a viaduct!

hope im on the right lines, if not i may just have a long lyin on saturday

No get up and go to do the exam!
You certainly seem to have grasped the issue.
The plan shows arrows in BOTH directions on both the Up and Down Valley Branch; that means RUNNING moves in each directions. The fact that a line might have an arrow only in one direction does not rule out a shunt route in the contrary one.

As you say the spec is clear re requiring standage in both directions on the DVB. This could be used for holding a freight train that has come from UM to be clear of the Mains when a train is due to come across the viaduct and terminate in the Branch platform for example. Indeed it DOESN'T require standage on the UVB, so perhaps the best thing is to do is put a main aspect with PL at 1750 rather than the separate GPL that my earlier post suggested. The plus is that it is simpler and you might be able to get O/L that doesn't conflict the the junction. [Note that although UVB is to be used in the Down direction it can't be for through freight as it has nowhere to run to- amy train must be for Branch platform or Up siding.] The minus is that the signal wouldn't be opposite that on the DVB that has been positioned for maximum standage and there could be parallax problems for curved approach leading to signals apparently swopping position as driver approaches- so if you are tempted to do this then put a proviso note re your assumption!


You are right that we don't want a driver to run too far on a PL aspect- it is unreasonable to get driver to run a long distance "as far as the line is clear" and it takes a long time. 200m fine, 400m if necessary, 600m if there is no reasonable alternative. However I didn't think anyone was suggesting crossing viaduct on a shunt aspect, though one of the earlier posts was perhaps a little unclear.

PJW
nthomso3 Wrote:I have had a private message detailing a mistake I've made but also will explain my thoughts a little clearer. If only everyone was willing to post publicly - we'd probably get a whole lot more answers.

Indeed a discussion group does require people to be willing to discuss! Interesting to have such a flurry of activity today; a few people on study leave just prior to exam I wonder?

nthomso3 Wrote:I made the mistake of including MAY-FA in the last post as I thought the linespeed is 120km/h but it's actually 140km/h so would probably just be MAR.

I believe points at 1320 are 40km/h (25mph) as I have found nothing suggesting otherwise. Hence the aspect reading over them reverse would need to be approach released if straight route speed higher by more than 10mph. However the UVB only reads over a similar speed turnout at 1750 or another one at 1900 to the fixed red at the right hand end of the UM platform [hands up- who forgot it?]
I'd therefore be tempted to define the speed in the Down direction of the UVB to be 35mph and thus get rid of the need to approach release the route from the viaduct to the DVB; after all that is the route that all the through traffic takes so approach releasing it delays traffic and indeed could give a SPAD risk due to drivers conditioned to it's last mninute clearance. Assuming the signal for that juction is actually on the far side of the viaduct any SPAD would be of high consequence, and frankly the sigmal so much prior to the junction that approach release really pretty ineffectual at controlling risk of driver overspeeding. [I haven't done this layout at all- I am just staring at a blank layout- but I am still wondering whether a signal leaving the viaduct at around 1220 would be a good idea as hinted at earlier]

nthomso3 Wrote:The other comment was in respect to the standage. My thoughts to achieve maximum standage was to have only a IPL on the exit of the branch rather than a main signal to eliminate the overlap. This leaves two options to getting a freight train into the down valley branch - 1. have a shunt route over the viaduct up to the IPL, or,
2 - a main route up to the station then a repelling move back.

If you mean what I think you mean then you are off-beam here. A running move MUST end at a main signal having a red aspect except in the limited case of a bufferstop light or a reflectorised stop board (typically in reception lines, entrances to depots etc). Not sure why you think that an independent PL would increase standage (the O/L need not be contained within the loop- it can extend outside it at the cost of being a bit restrictive whilst a train is running in but then release once train timed to a stand). Of course nowadays on NR we often provide O/L beyond GPL signals anyway!

Aah, now I see where Astubbs comment re PL move over diagram came from. No, I agree with him; you wouldn't do that. Can't say I totally follow your wording about getting freight (from where?) to the DVB (which bit?). I think you are on the wrong lines here anyway...

PJW
probert1 Wrote:Down Valley Branch to Station C
My min SBD for the Branch lines is 772m and max 1025m. Would it be possible to place a main aspect on the Down Valley Branch at say 660m and then place a signal on the bi-directional Down Valley section at around 1780m. Obviously slightly overbraked, but it would allow freight to be run right up to the Switch diamonds and held there. Standage would be limited as Peter previously mentioned. A sub signal provided with the main aspect at 1780m would then allow facilite a shunt move into the station area.

I assume that you are saying the max is due to being 133% overbraked and that the constraint imposed by headway is less onerous. Placing signals as you suggest would be 145% overbraked; yes this is something that could well be acceptable [NB although the Group Standard indicated 133% this is actually often not achievable withou compromising other standards and good practices. NR does hold a general non-compliance allowing, in suitable circumstances, greater overbraking. Interestingly the former standard was 150% which may indeed have been a better balance between overbraking risk and practicability; it is probably more important for spacing along a route to be CONSISTENTLY overbraked rather than limited to any specific value.

I think though that I'd be tempted to place a signal on the DVB that is overlap clear of the single line, say perhaps at 490. This is more operationally flexible, though with a large risk if SPAD not contained within overlap- certainly need to ensure that good TPWS provision. I have already mentioned possibility of a signal at around 1200m, so to get braking distance in then the previous signal would have to go at 425 rather than the 490 suggested- a longer overlap so a better chance of stopping a SPAD so that is good. Obviously there wouldn't be braking at 100km/h to the signal proposed at 1780 but of course in reality there is the 40km/h restriction over the points to observe. Hence if we defined the speed of that section of the DVB between this turnout and the switch diamonds to be 35mph it wouldn't actually impact on the real maximum speed of trains along this section. Therefore I'd be looking to define that as the speed in the down direction from somewhere along the viaduct to the junction at station C. Not only does this get rid of the need to approach release as discussed earlier but also would no doubt give me enough braking at the redefined permissible speed to my signal at 1780. [NB I am NOT suggesting proposing speed restrictions that actually change the speeds that trains could in reality travel; only adjusting the theoretical speed limit to be consistent with that which trains could in practice attain, given known acceleration / braking and existing adjacent restrictions, in this case over curved path of turnouts]


Who says you need a shunt route / aspect into the station; you may have a need to shunt an ECS into the platform but it could use a main aspect as there is no stated or implied requirement that I have found to go into occupied platform.

probert1 Wrote:Station C to Down Valley Branch
A PL at Station C (DOWN MAIN) platform would then permit a shunt move onto the bi-directional Down Vally Branch. A main aspect placed at 1400m would then allow any freight standing to be signalled across the viaduct to the Up valley Branch.

Again why do we need to signal a train onto the DVB when it is occupied? A main aspect would do.

PJW
What a last minute flurry; hope I haven't missed anything in all that lot!

If so then please raise again, but SOON!
Don't forget that Forum will become unavailable prior to the exam in the UK because the time zones around the world differ!

PJW
I have a sneeky feeling that I should have used this forum about two months ago, oh well, there's always the Natural History museum if I finish early....!!!
Attached is an attempt which I have recently received for this layout; for those with access to the sub-forum note that an alternative solution to this same paper has also by coincidence recently been posted there.

This attempt has adopted a 3-aspect solution; although this is argued just to meet the headway requirement, it would probably have been a good idea to have used some 4 aspect signalling in the vicinity of the main station in order to have permitted sensible signal positioning and being able to achieve the requested standage and other operational requirements. Alternatively some additional 3 aspect signals could have been used but with suitable approach release ("modified 3-aspect sequence") so that adequate warning of stop signals could be given to the driver. However even without looking in detail at the particular layout constraints I think that the calculations showed that spacing signals within the min/max criteria for 3-aspects would be improbable in anything but plain line.

Overall it shows a reasonable level of completion and that the candidate has got he general idea; however there are quite a lot of errors, some particularly serious, some pretty trivial but demonstrating a lack of attention to detail that could so be easily have been learnt. In particular it has not addressed many of the specific operational requirements.

Therefore I doubt that it would rate a pass- there are just too many defects which seem to reveal that the candidate has not really understood all the concepts nor actually prepared for the exam adequately. However it is not hopeless; the candidate is actually a long way there and just needs to address their areas of weakness in order to be able to pass.

There are 25 days left; you'd probably get your car serviced before putting it in for an MOT, so if you don't want to suffer an avoidable failure yourself then make sure you schedule an adequate pre-exam check-up to tighten up on a few things that might otherwise let you down........
Hello,

Does anyone know which UK document I can refer to in order to determine the type of level crossing to be used in any layout which in this case is the 2007 mainline layout? The layout states that the level crossing has 500 road users per day. I have gone through the Railway Safety Board's Guideance document GN0692 but cannot find anything.

Or is it a case of looking at the layout (in this case a single line), the frequency and speed of trains running up and down and the then justifying it whether it should be an ABCL or AOCL not to mention whether it is manned locally or remotely.

Look forward to comments on this please.

Thanks


Alex
Dear all,

Found the answers in Railway Planning & Safety Guidance 2E on Level Crossings

Cheers

Alex
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