(30-09-2010, 05:39 AM)alexgoei Wrote: Hello PJW,
Thank you for the reply
Sorry to belabour the issue concerning MAY-FA but the second row does mention permissible approach speed of 40 - 75 mph (64 - 120 km/h) and divergence speed of 25 mph (40 km/h).
Cheers
Alex
So it does- my apologies.
Standards change and one ends up not knowing what one thought one knew. In reality I think that recent change has been made particularly for getting a freight train off the main line into a Goods Loop faster, but yes it does seem that your solution is compliant and I was wrong. One advantage of having to learn from scratch is that you read what is written, rather than being pre-conditioned by previous knowledge and experience. I certainly haven't encountered a flashing aspect in such a scenario, but perhaps this will become the way of the world. In my defence I think that if you look at the compliance clause of the instruction published in September 2006 that it would NOT have been applicable for a layout signalled at the very beginning of October 2006 (joke!)
One problem that you have to face is the examiners might take exactly the view I did, but without the opportunity to discuss afterwards. The mindset of presenting a candidate a layout with certain turnout speeds higher than most others certainly suggests that they are expecting the signalling to be different........... I think I'd still advise caution over what may be seen as the overuse of flashing aspects. [There are risks associated with MAR and risks associated with MAY-FA which are hard to balance; I believe that one of the motivations for NR to amend its standards has in fact been commercial pressure from the train Operating Companies- compare the wording agasinst that of the older Railway Group Standard that is still in force].
I think where the turnout speed is as low as 25mph which as you note is the minimum permissible speed, you really need to consider whether you would provide MAY-FA. Whereas it may be compliant to do so that doesn't actually mean that it is appropriate. I think in that case I wouldn't depict it on the plan but add a note that it could be an option. If you provide in such circumstances then probably worth a note that it is compliant and quote the standard number, so the examiner is perhaps jogged into looking it up rather than relying on their experience!
PJW