(14-06-2010, 05:57 AM)greensky52 Wrote: Just back from weekend, it is so appreciate that you gave so detailed explanation for all of my questions. Forgiving me as a new man in signalling discipline... I need some time to comprehend all your explanations completely, and I think I also need to discuss these with my colleague, helping me understand all the meanings you mentioned. Thank you again... Later I will discuss with you if there is still something confused.
OK take your time. Yes it is often a good idea to talk through wih someone else face-to-face.
Quote:Furthermore, referring to your answer of point211, item 2: I do not think 212 is trailing point in overlap of 142, because 142's overlap is EK, but 212 is in EL. Do you think EK and EL both are overlaps of 142?...
(12-06-2010, 10:36 AM)PJW Wrote: 211 Item 2
The particular issue:
a) My assumption is that the switch tips of 212B would be some 5-10m to the left of the post of 142 and that 212A would be perhaps 50-60m from 212B since most single slips are quite tight.
b) 211 is not a facing point in a swinging overlap beyond 142 so there is no requirement for time of operation locking here; you are quite correct
c) 212 is a trailing point within the overlap beyond 142 and 211 is providing both flank (212B) and trapping (212A) to that overlap; therefore they must be locked whilst the overlap is required. Once however route 146 has been cancelled AND its approach locking released AND the route locking on track ES has been normalised AND the berth track ER has been occupied for long enough to have proved the train at a stand, then the locking can be released.
d) Distance from 146 to 142 is 650m and I assume ES to be 180m since it is an overlap track; therefore ES would be 470m long. Hence I'd put the time more like 47 sec than 30 sec which is too short and applicable to a much shorter berth TC (see timer values ) but since it isn't completely rediculous for the principle of such a control then I don't think you'd lose many marks for the wrong time
A route set from signal 142 to 146 reserves the railway
a) for the route itself (post to post) = ES, ER [because that is the distance over which the train is authorised to move]
and
b) the overlap beyond 146 to the marked overlap joint (or joints if there are alternative positions beyond facing points).
[because we wish to mitigate the risk in the event that the train fails to stop exactly where it ought to and therefore provide a safe overrun length]
In this case there is one extent of overlap; it is the joint at the left hand end of EK. There is one overlap which is the combined length = EL, EK which is a total of 200m beyond the signal. Hence 212 is within the overlap.
Quote:As you mentioned above, I attach my attempt on Point 203 & 211, which were finished last week, before getting your explanation...so there were still some errors we juse discussed, please do not mind...
I'll look at in the next few days and then respond; I note that you did before recent comments.
PJW