16-02-2009, 11:12 AM
Peter Wrote:I've done some jottings that are in the attachment here and I tend to agree that 4 aspect on the main line would be necessary and even at minimum braking, you only deliver 100s so any variation does eat into your contingency.
For stopping calcs, I've employed the "how much time does a stop add into your front train" approach. ie take your NS headway and add time for deceleration, acceleration and dwell and see what you get, using line speed for all of this (assuming your fast is bearing down on you like that) but then converting the distances to time using headway speed to give a worst case (discuss!) you get 230s.
I was working on the 2009 Study Pack over the weekend and am putting ETCS information into it and may even attempt the 2008 layout as Level 2 withou signals.
I started by attempting to address the braking and headway calcs; I don't know what the examiners would expect (I suspect they have no idea either) so I have made a stab that I'll probably ask them how they'd rate. Problem is you either say "Not applicable to ETCS" that sounds like a get-out and isn't really true anyway (so how could they award marks) or you go into a lot that they may give no credit for (the precise question as asked is not sensible for ETCS, the constraints are not to do with braking and most of the constraints are not associated with "Signalling the Layout"......)
I'd appreciate comments on my approach (EVEN IF YOU DON'T KNOW ETCS THEN YOU CAN FOLLOW MY REASON, ENSURE LOGIC WATERTIGHT / EXPLAINED AND CHECK MY MATHS). I followed a similar approach to Peter re the fast train catching up the stopping train, but felt that the question meant that even the non-stop are only scheduled to run at 140km/h not the 160km/h that Peter assumed.
PJW