2007 Mainline layout

[PJW]

Dear PJW,

This part contains the cover notes, the stopping and non stopping headway calculations, the method of achieving the freight train standage as well as paths for the engine to move around the Down Valley Branch and the selection and calculation on the type of level crossing, AOCL.

Cheers
Alex

Only real comment on the non-stop is that your English is a little confusing when you say "if 3 aspect signals are used theywill be spaced at 1305m, however this is less than the SBD".
this implies that you feel it is a trenable solution.
I think you meant to say: [i]
"If 3 aspect signals were spaced to provide the headway they would need to be 1305m apart but this is not acceptable since this is less than SBD and therefore this possibility is discounted"[i]

The other comment (given that I see that you have placed some 3 aspect signals on the layout) is to take the approach os assuming 3 aspect signals spaced at SBD and seeing what that gves you as a headway. Whereas SBD is irreducible (unless get agreement to change permissible speed of the line), headway is often more aspirational and therefore negotiable.
Particularly on a line with this amount of traffic, then 20% contingency when designing technical headway is rather over generous. If you went to the client and said that if they could accept 115 sec technical headway but this would permit the use of 3 aspect signals that would save worthwhile money, then you may find that they may decise to waiver any contingency between the design and operational headway- after all we only seem to have at most 8 trains per hour, so there is a lot of contingency already built into that 120sec requirement isn't there?

Stopping headway
Yes presentation has improved; just hope that you can reproduce in the exam without the Excel spreadsheet!
Worth mentioning that a major reason for the contingency in this case is the fact that your calculations do assume driver only braking for the station very last minute and therefore in reeality is likely to take a bit longer as likel to be driven rather more cautiously.

Also worth a statement that a restrictive aspect seen at signal 5 is not considered to affect headway given that the driver will be focussed to stop at signal 7 regardless of the aspect at 5 which is therefore irrelevant.

Your final paragraph ought to make cleare that the signal spacing is determined by the mre restrictive of the two maximum requirements; it reads as if there are two separate signal spacings!