29-12-2011, 12:02 AM
This is an interesting scenario; rather more involved than is typical for IRSE module 2.
Given that the scenario has ore and wheat trains, I am guessing that the exercise might be one set by the Queensland University open leanning course; if this is indeed the case it might be inappropriate that I commented in detail.
However it is correct that the signalling would have to reflect all traffic permitted to use the relative portio of the layout and the stopping distance of the ore trains exceeds that of the passenger service and therefore must dictate the signal spacing. Indeed althoough from a headway perspective the wheat trains are all but irrelevant (versy sparse, only short "season") they are still relevant for braking distance considerations.
So in part b) when considering the 4 train/ hour, why did you use 700m as the signal spacing, when in part a) you correcty pointed out that the braking for the ore trains would require a signal spacing of at least 830m?
Your comment re the "workable headway" is valid, but I'd have expected the answer to have been based on one specific railway's practicesa as assumed by the candidate. However the distinction doesn't seem of significanc,e given that you state headway acheived is 92 seconds when the timetabled requirement is only 4 trains per hour and there appears not to be a required non-stop headway explicitly stated. Was there in fact a need to undertake these calculations at all?
As you have recognised it will be the 3 min stopping headway requirement that will dictate (but of course this should also have been undertaken with signals spaced appropriately for the ore trains...)
Given that the scenario has ore and wheat trains, I am guessing that the exercise might be one set by the Queensland University open leanning course; if this is indeed the case it might be inappropriate that I commented in detail.
However it is correct that the signalling would have to reflect all traffic permitted to use the relative portio of the layout and the stopping distance of the ore trains exceeds that of the passenger service and therefore must dictate the signal spacing. Indeed althoough from a headway perspective the wheat trains are all but irrelevant (versy sparse, only short "season") they are still relevant for braking distance considerations.
So in part b) when considering the 4 train/ hour, why did you use 700m as the signal spacing, when in part a) you correcty pointed out that the braking for the ore trains would require a signal spacing of at least 830m?
Your comment re the "workable headway" is valid, but I'd have expected the answer to have been based on one specific railway's practicesa as assumed by the candidate. However the distinction doesn't seem of significanc,e given that you state headway acheived is 92 seconds when the timetabled requirement is only 4 trains per hour and there appears not to be a required non-stop headway explicitly stated. Was there in fact a need to undertake these calculations at all?
As you have recognised it will be the 3 min stopping headway requirement that will dictate (but of course this should also have been undertaken with signals spaced appropriately for the ore trains...)
(28-12-2011, 03:34 PM)onestrangeday Wrote: Hi Signalling Professionals:
The attached files are my another try for the headway and signal spacing calculation for a mixed line railway network.
Please check my work, any comments or suggestions are highly appreciated.
PJW