2013 Aspect Sequence

[asrisaku]

Dear PJW

Could you please check my attempt on aspect sequence 2013?


Best regards
Arnut

[dorothy.pipet]

I've just had the quickest of looks, maybe I'll have a chance to look again later (but more likely PJW will get there first). A few things:

I can't see where you've said what signalling practice you're using so I've assumed UK mainline?
In which case it's not usual to put route identities on the chart.

Consider why you chose 4 aspect signalling - I would say it's not needed on the branch (signal 31) and you'd need to say why you want it on the Down main, when most of the signal spacings are adequate for 3 aspect signals.

Have you considered how trains can be signalled into the siding? (I'm noticing this myself because I nearly missed it in the exam last year!)

[asrisaku]

Thanks Dorothy for your time and your value comments.

Regarding the first comment, I didn't aware that and I am using UK mainline principle.

#2 Is there any concern with 4 aspect signal at Signal 31? Can you help explain 3-aspect signal and 4-aspect signal with the long run? Any difference? If I understand well the signal that goes to line block, it's usually 3-aspect signal, right?

#3 the principle for siding and UP/DN main is the same or not? What should I have done in this case?

[dorothy.pipet]

My knowledge/experience is all UK mainline practice; in the exam you should apply your own knowledge/experience and state which railway that is for.

#2a With respect to the down branch, the braking distance is 400m and the next signal is 5km away. When we're using 3 aspect signals the minimum spacing is braking distance apart. There is also a maximum to avoid driver complacency. This is when a driver knows the signals are further apart and delays applying the brakes, but delays too long so cannot stop at the signal. We often use 1.33 x braking distance for this maximum. Consequently the signal spacing on the branch is too long for 3 aspect signals: the branch must use 2 aspect signals, thus, Signal 31 would be a red/green 2 aspect signal.
#2b Looking at the braking distances on the down main, I think most are within the range for 3 aspect signalling, there is just one that is too short. The examiners want to see how you cope with that complexity, and there is more than one "correct" method.
#3 As far as I can see you have not provided a route into the sidings. Where would you approach them from - signal 15 or 23 or both? What type of aspect - perhaps a shunt route so a subsidiary aspect?
#4 Which leads me to realise that you have illustrated a subsidiary aspect on signal 13 but not explained it.

[asrisaku]

Actually I am familiar more with mass transit system. I was a tester in mainline project in SRT(State Railway of Thailand). However, I think it would be better to refer UK mainline practice because there are plenty of sources and information to learn and study.

#2a Breaking distance is only 1.33x400 = 532m and the next signal is 5Km then we need to have a red/green 2 aspect signal. Am I right? otherwise the driver will delay applying the brakes. Then the signal 31 should have been R/G signal.

#2b This is unclear to me. Please help explain that.
Consider breaking distance 1000m from mainline and 1.33x1000 = 1330m then
for example the distance from SI11 to SI13 is only 1100 which is not enough and unable to apply the brakes with sufficient distance.

#3 Yes I have missed the routes going to the siding. Then I'll update my aspect sequence.

#4 I saw ROL and I realise that probably there is a need for a shunt route to display in the aspect sequence.

Thanks

[dorothy.pipet]

For Aspect Sequence information I suggest you have a look at the Study pack for Module 2 (Aspect Sequences used to be part of Mod2). PJW has put a vast amount of information in that which is not just for UK Mainline. It will probably help you out with Aspect Sequences from a Mass Transit perspective.

Looking at our points from a UK mainline perspective though ...

#2a correct.

#2b For 3 aspect signalling, the yellow-to-red distance should be _between_ [braking distance] and [1.33xbraking distance]. In this case 1000m and 1330m. Now look at all the signal spacing on the mainline: mostly it fits this but there is a problem: Route 13A(M) to S15. This can be done with an "isolated 4-aspect sequence" or by approach controlling that route, for example.

#4 ROL is for a warner route, which is a delayed yellow as your aspect sequence shows. Shunt is a different class of route, and the aspect's meaning is not listed in your answer. I therefore think you are a bit vague on Warner, Call-on and shunt routes?

Hope that does not confuse you too much.

[asrisaku]

Please apologize my queries.

#2b If signal 13 is a 4 aspect signal, the breaking distance is still over limited? SI13 as yellow to SI15 as red is still required the breaking distance between 1000 and 1330m. How to cope with that?
I decided to design SI11(4aspect) instead. Please see my attachment. Do you agree with me?

#4 Now I have seen another mistake. SI23 should represent shunt symbol with a route indicator, right? SI13 should not have had Shunt symbol.

Deeply appreciated

---

Dear Dorothy

I have done new aspect sequence after ur comments. I will be able to upload it tomorrow. Please kindly check it if possible.

I just did some research warner, shunt and callon routes. I was confused and stunned with the unfamiliar question and finally mixed up with warner and shunt. Thanks for helping me out

With regards
Arnut

[YENDRI]

Dear Dorothy,

I just have a quick a look an update of step down char from Arisaku.
From the step down aspect chart it show that signal 13 B(M) possible to present G+J14 if 23 route C(M) green or yellow.

I'm wondering whether if that possible to have Green aspect lights if the route run to the turnout? as we see that to the loop speed are for 50 km/h and with braking distance 150m.

Thanks and look foward to your guidance.

[asrisaku]

Dear Yendri

Maybe wait for signalling experts to explain. But in my opinion, we have same speed for turnout and loop line. This does not require MAR. And in your case if we have speed turnout and loop line very big different, it will be your case.

I suggest you maybe read this thread. Perhaps it helps

http://www.irseexam.co.uk/thread-393-pos...ml#pid5293

Note: my second attempt seems not correct. Tomorrow I will upload it with new one that makes more sense with the braking distance because I provided overbraked at signal 11 which I believe it is wrong YY -> R 1850m beyond 1.5BD. And also signal 13 is underbraked Y->R 750m which is not enough for BD 1000m.

Best regards
Arnut

[Peter]

Dear Dorothy,

I just have a quick a look an update of step down char from Arisaku.
From the step down aspect chart it show that signal 13 B(M) possible to present G+J14 if 23 route C(M) green or yellow.

I'm wondering whether if that possible to have Green aspect lights if the route run to the turnout? as we see that to the loop speed are for 50 km/h and with braking distance 150m.

Thanks and look foward to your guidance.

Yes, in UK practice, the aspect displayed only gives information about the aspect ahead and does not convey any information about the speed, so even though the route from 23 is a relatively low speed, you can still have a green aspect in 13 (once the MAR condition has been met) and 23.

Does that answer the query?

Peter