IRSE Study Pack 090131 - Appendix G22 and 2004 Paper

[PJW]

2 Specifically for the 2004 paper, the requirement for this paper would be to calculate if the non-stopping and non-stopping headway can be met. For the latter, to look at the section of the line where meeting this requirement is the most onerous. Am I correct? (although I am still trying to identify where this section is)

The actual question paper wording was:

Question 1
Determine theoretically, either by calculation or graphically, appropriate signal spacings for the braking characteristics and the intensity of traffic on offer. All calculations and graphs must be shown.

The layout paper asks for
a) "following fast" which is definitely meaning non-stop headway at 100k/h and
b) "following stopping" which I interpret as one stopping train following another stopping train- I think the wording isn't 100% unambiguous though so I'd state my interpretation on the paper.

So it is asking you to calculate what signal spacing (which also is compliant with the need for adequate braking yet not too excesssive) just satisfies the more onerous of these two requirements and then design the layout accordingly.

The whole point about non-stop headway on the main line is that it is constant speed, steady state so it is the same everywhere as speed of line is constant. Stopping headway pinch point is certainly station D because trains are stationary for 30 seconds and also be slowing prior and accelerating after. Also note that there is a stopping train service from A and from C that have converged by then.

So work out what signal spacing you need to satisfy the non-stop then put a few signals on the layout (you virtually have to have one at the exit of the platforms on both lines) and see if that delivers the required stopping headway.
Just taking a very quick look- through train 2.5min headway, dwell time 30 sec so have got 60sec for addditional time for stopping train re slowing down / speeding up. 100km/h around 30m/s and at brake rate of 0.5m/s/s takes 60sec to slow, similar to speed up. Comparing to a non-stop means that travellling at half speed so will lose 60sec compared to it. Hence obvious that the two constraints in this particular example are pretty comparable. Hence I'd put the signals before and after the station starter at minimum spacing and then do the sums to demonstrate would achieve the stopping headway requirement.
Does that make sense?