2006-Aspect Sequence Chart

[PJW]

Dear PJW

I will review my attempt as suggested in your comments. I am not sure I fully understand the aspect sequence.

A stuck question in my mind, why doesnt the aspect sequence show callon routes? I could not find the reason behind.

Thanks
Arnut

Call on moves are almost always approach released from red and hence there is no relevant main aspect sequence up to a call on move that differs from the aspect sequence to the main signal associated with it being at red. The call on being shown is not dependent on the aspect of an exit signal (indeed there is not really and exit signal since you expect the section to be occupied). Showing call ons therefore adds nothing on the aspect sequence chart.

Peter

Completely agree with Peter. However note that Network Rail has taken to wanting such diagrams to denote every aspect even though there is NO SEQUENCE to depict. Hence in the real world to conform to their standards one does have to do so, even though it justs adds clutter and uses space better devoted to the meaningful stuff.
I do see some value for showing the PLs associated with main signals that provide the ONLY route to a destination (particularly where this is onto a Branch rather than just merely into sidings) but not permissive moves into platforms etc where there is a main aspect movement to the same destination. I suppose I regard this as a "positive statement" that there is no sequence associated with a running move that might arguably have had a maain aspect move provided.

In the IRSE Exam be careful to read the wording of the particular question for that year to ensure you produce a chart scoped according to those instructions.