1998 calculation and layout

[greensky52]

I have tried the calculation and layout of year 1998, and have some confusions as follows:

1. Usually in non-stopping calculation, we leave 20% contingency. But I noticed people do not leave contingency when calculating stopping headway. I think it should also leave 20% contingency although I did not do so in this practice

[greensky52]

Continued (for the limit of attachment)

[PJW]

[quote='greensky52' pid='1683' dateline='1277368019']
I have tried the calculation and layout of year 1998, and have some confusions as follows:

1. Usually in non-stopping calculation, we leave 20% contingency. But I noticed people do not leave contingency when calculating stopping headway. I think it should also leave 20% contingency although I did not do so in this practice

[PJW]

[quote='greensky52' pid='1683' dateline='1277368019']
I have tried the calculation and layout of year 1998, and have some confusions as follows:

3. In the mod answer, I notice he uses 3 aspect in station E, I agree. However, he uses 4aspect around junction D and F while using 3 aspect in straight line, eg section A & H. My view is it should use 4 aspect in straight line without any junctions and stations, but using 3 aspect in those lower speed area. But the mod answer seems showing the contrary meaning. Am I wrong again? Or is it his error?

4. I have reviewed the model answer in study package, and the layout shows the signal spacing distance for 3 aspect or 4 aspect may be 1000m or more, but according to my calculation, the signal spacing distance for 3 aspect is between 773m to 868m, and 387m to 515m for 4 aspect? It is impossible for a signal spacing bigger than 868m

[PJW]

5. In Up Goods and Down Goods area, mod answer uses a shunt signal 307 and a main signal 132 in Up Goods, but main signal 137 and 134 in Down? I think these 2 situations are same. I think 134 should be a shunt signal because the movement is wrong direction. What about your view?

I agree with the layout as drawn, but it was a very good question to ask. You correctly identified that 307 is appropriate as a shunt signal for a light engine movement within the station area whereas 137 needs to be a main aspect as it is for a running move for a freight train proceeding along the line. You didn't understand why this same logic doesn't apply at the right hand end. What you missed was the note that freight from G to H reverses at E. You need to work out how to provide the signalling for this to occur. We need to bring a train in on the Down Goods and stop it at 137. Uncouple locomotive, then clear 137 for it to continue along on the down until it can get behind 312, , 312 routed via one of the different ways to single the loco in the up direction until it can get behind 301 (depending on the railway's rules perhaps the driver needs to change end to the other cab, but in some circumstances may continue to drive from what has become the rear cab). Then from 301 back onto its train that was left on the Down Goods, couple up again, then driver's cab is at 134 and is then routed to junction F in order to continue its journey on the other line from the one on which it arrived. Hence 134 is not for a shunting move but a running move after train has reversed direction. Your thinking was right as far as it went; but it hadn't gone far enough.

[quote]
6. I put a main signal between point 203B and 204, but the mod answer put signal 205 which I think having the same function as mine. I think it should not put a stop signal in the tunnel, so I put it at the exit

[PJW]

[quote='PJW' pid='1693' dateline='1277502369']
[quote='greensky52' pid='1683' dateline='1277368019']
6. I think it should not put a stop signal in the tunnel, so I put it at the exit

[PJW]

[quote='PJW' pid='1693' dateline='1277502369']
[quote='greensky52' pid='1683' dateline='1277368019']
6. I think it should not put a stop signal in the tunnel, so I put it at the exit

[greensky52]

Sorry to reply you so late because I have reviewed the Study Pack and related materials carefully for better interpretation. Anyway, first of all, thank you a lot for your careful answer. I read your state comparing with the Study Pack, and has some confusions again:

In Study Pack AppendixW Activity1C: at last part of stopping headway calculation for Up Main, it says "To achieve the stopping headway, this signal would also have to be the first cautionary aspect, and hence 3 aspect signalling is appropriate(at least in the station area)". But I did not find any hint about why choosing 3 aspcet signal.
And 59s is for the train from 1st cautionary signal to stop signal, but I think it should also contain the constant speed section from the green signal to 1st yellow signal. Where is my error? In other years' stopping headway calculation, the headway usually contains 5 time section, but this only contains 4. So I am very confused why does this not contain the constant speed section...

Non-stopping calculation also uses 3min headway, but the required haedway is "Main Lines: following stopping at 80km/h"--I think it refers to stopping headway only. I am confused about why you take non-stopping and stopping headway both as 3min? I know, this situation is uncommon in other years' exams, which always have different headway for non-stopping and stopping.

Also in study Pack AppendixW Activity1C, Approach to Platform5(Up Main): it says an allowance of 111s for the time between Green and Red, and time taken to traverse the 40kph section is 35s, reducing from 80kph to 40kph is 22s, so leaves 54s at a constant speed. But I think it also should minus 12s sighting time...

I do not have much experience in railway work, so most of knowledge comes from books only...lacking of real experience

[PJW]

In Study Pack AppendixW Activity1C: at last part of stopping headway calculation for Up Main, it says "To achieve the stopping headway, this signal would also have to be the first cautionary aspect, and hence 3 aspect signalling is appropriate (at least in the station area)". But I did not find any hint about why choosing 3 aspect signal.

The Study Pack says: [i]
Assuming a platform dwell time of 30s (pessimistic since other platforms are available), and a sighting time of 12s, this leaves 150

[PJW]

I think it is best that we look at your calculations first . For the moment I shall leave discussing your layout and the suggested model layout but will return in the future.

Herewith some comments.

Good level of completion and much that was right; however also many things which weren't good either. Actually it was some of the more simple things that let you down- knowledge of the correct symbols to use rather more than fundamental signalling misunderstanding I feel, though there were a few examples of those as well.

Hence have tended to concentrate my comments at picking up a lot of generally small things (that in total significantly detract from the impression) in each locality, rather than discuss in depth the signalling of this particular layout since these are the things you need to concentrate on first.

It was certainly a very useful first attempt though; broadly along the right lines- very inital impression was that it looked good but it lthen ost its shine when began to look in more detail.
The good news though is that you have a clear picture at what you must aim to produce in the exam; a lot of people have difficulty in getting started at all but you launched in. The result is that you have produced something substantial enough for me to get a good idea of what things are going wrong. Hopefully you can now take these comments on board and eliminate many of these bugs; if so your next attempt should look much better.