Aspect Sequence exercise

[onestrangeday]

Hi PJW:

thanks for your review. You have mentioned about the attachment, but I don't see it.

I have few questions though:

"a) 11 is shown as a Red/Green not far in rear of 15 (similarly 13 and 17). Probably best not to provide 11- there is no absolute need to have a platform starting signal. If really need 11, then would need to make it "preceeded" bt 15; i.e. prevent 11 for clearing unless 15 already cleared."

Q1: If in this case the platform is very close to the points area, can I eliminate the junction indicator, instead place at the platform with the starting signal ?

or if you eliminate the platform starting signal, how do you show to the driver when to proceed ? (how does this done in UK ?) with signs, or order from train controller ?

Q2:
"I have shown on the attachment how to show the "MAR" Approach Release from Red for those routes which are the slower speed divergence through points."

what is "MAR" Approach release ?



thanks

I think it is easier to discuss the single track layout; the double track layout as drawn has some signals which are underbraked (and indeed others which appear overbraked); it would be best to get to grips with more straight forward arrangement first.
The only issues on the single track layout are:
a) 11 is shown as a Red/Green not far in rear of 15 (similarly 13 and 17). Probably best not to provide 11- there is no absolute need to have a platform starting signal. If really need 11, then would need to make it "preceeded" bt 15; i.e. prevent 11 for clearing unless 15 already cleared.
b) 55 should be a Red/Yellow rather than Red / Green and there should be a red light at the buffers.

I have shown on the attachment how to show the "MAR" Approach Release from Red for those routes which are the slower speed divergence through points. The really important thing to understand is that the signal is at red until the train has passed the previous signal, so the driver will see a yellow there.

I have also drawn out the area around 15/17 to 23/25. On your diagram, can't tell really what is an approach release and what is a pure sequence.

I'll perhaps annotate your examples when I get a chance, but you need to show a transition from one aspect (say red) to a better aspect occurring and against this show the condition which triggers this change. These are shown as vertical lines (and is another reason for drawing the sequence lines horizontal and diagonal rather than vertical)- to distinguish more easily my preference is to show dashed. You will find several examples of this in attachments in other posts in this topic area.

Just a quick initial glance of the presentation of sequence on screen without checking to layouts suggests are on right lines; nothing too awful such as a Green reading up to a Red.
Two things that immediately strike-
1. You have not shown any approach release. Where the speeds of a diverging route is different from the straight route, then the signal must be held at red (or in some specific cases at yellow) until the train has got sufficiently close so that driver can see both the route indication and the actua colour of the signal aspect- certainly needs to have received a caution aspect on the signal prior.
2. An aspect sequence chart is easier to read if you avoid depicting the lines completely vertically, but slope at a slight angle. Much clearer that chart reads right to left or left to right; also twhat is a "convergence" from two parallel signals in rear or what is a spreading out to reflect multiple routes from a junction signal. In particular on oe diagram you have joined both categories of the above in the same vertical line. It isn't actually incorrect but since the whole purpose of such a diagram is to give a pictorial readily assimilated depiction of the sequence, it rather loses the whole point if need to study hard to work out what is happening. In reality no real problem on such a simple layout, but as a matter of principle for application to more complicated sites then it is an important consideration. [Note that you will find many sequence charts on modern prjects do use the vertical lines- this I think happens because it is easier for the designer using CAD and saves a little space, but as a user it is definitely unhelpful, so much so that the diagrams rarely get used and everyone refers to the Control Tables- the easy to understand presentation showing the "whole picture" just fails to achieve its end and in my opinion we might as well not have them!]

Hi Signalling Professional:

This is the first time I have tried an exercise for aspect sequence (single line and double line layout which I have done earlier) . can someone check my work ? and I would like see whether I am on the right track or not.

thanks