24-06-2010, 07:14 AM
(23-06-2010, 07:30 PM)KonduriRaghavakumar Wrote: Actually i did not have any idea about the braking distance and time calculations I recieved the study pack from IRSE and I gone through it upto now and just attempting this appendix left over question. please tell me is the method what I adopted is correct or not?
Broadly but not exactly.
Q8 was in fact a hard one to do as your first- the others had left it as being "too difficult" I expect!
It is actually a "double" one because there is a requirement to satisfy for passenger trains by day and a DIFFERENT one by freight trains at night and the signalling designed needs to respect the requirements for BOTH. So there are two braking distance constraints that define possible minimum spacings (and when considering degree of over braking the associated maximum), two headway constraints that define possible maximum spacings. Your task is to see what the smallest minimum and the largest maximum is, in order to determine the acceptable range of spacings for your signals.
I don't think you "saw through" the question to appreciate that and hence the figures you used in your calculation mixed some things from the two scenarios.
Otherwise in outline you were putting numbers into sensible formulae; not quite sure where the 155sec required headway figure was derived from even using 25% contingency. You generally seem to have used figures relating to the passenger train so the stated requirement was 120s; if you wanted some contingency then you'd need to be designing signalling to do BETTER than that, say 110s or 100s. If you design for 155s then you will fail to deliver the train service even if it is otherwise running 100% to time at the commencement of the area of your signalling.
Suggest you rework your answer to Q8 in the light of the above whilst I take a look at the remainder of the questions (but the stopping looks pretty good at first sight and you made a good job of the drawing!)
PJW