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+---- Thread: Miscellaneous queries re Signalling Layout (/showthread.php?tid=278)
Miscellaneous queries re Signalling Layout - PJW - 02-09-2009
Quote:Dear Sir,
I have some very basic doubts.
Kindly clarify the following,
#1 Length of Passenger train is 200m( which includes 2 locos), similarly the length of freight train 400m (which includes 1 loco) - Is it so?
Passenger train is unlikely to have 2 locos; actually probably they will have none. In the UK the majority of train are now multiple unit stock where the traction is incorporated into the passenger carriages having cab at each end. Reasonable assumpton to make (STATE IT!) unless there is some info to the contrary.
Freight trains of 400m long can be pulled by one modern locomotive; however if older locomotives then several would be needed working in multiple
Quote:#2 While performing a run round movement or reversing move, if the standage of the line is say 400m, then how it can be done for a freight train of length 400m
It can't. If you have a requirement to have standage for a 400m train (which I am assuming is 20m loco and 380m of wagons) and also a requirement to run around then you need an absolutely bare minimum of 420m (i.e the 20m loco at the other end). Really I'd say you need at least 450m thus allowing the driver initially to stop some 15m short of the signal, uncouple, use the run round loop and attach to the far end of the train and still have 15m from what will now become the front cab (on the assumption that train is to be hauled in the opposite direction rather than being propelled back into a dead end siding). The IRSE layouts are often very "tight" and may not make this possible. Treat it as you would a real job; the client may have a lot of demands but it is not always possible to satisfy all of them for a cost that they consider acceptable; if you feel that you would need to limit the maximum length of a train to 350m in order to run round safely and efficiently then state your reasons and signal accordingly.
[The other option that you could offer the client if they really insist on having a train longer than that which the track layout is comfortable is that they will have to issue operating instructions that after the train has stopped then the exit signal is to be cleared and the train pulled forward so that the loco passes the signal and stops with its rear end/ start of the wagons just at the signal. Then it is uncoupled and loco runs around and backs onto its train. This saves the 20m loco length and the 15m defensive driving / stopping inacuracy allowance at the other end. However it is a cumbersome arrangement and risky if the loco moves the train back slightly when it recouples / does a brake test since the rear end is invariab;ly very close to being foul.]
Quote:#3 If a signal is placed within SIP what will be the normal aspect of the signal.(For AHBC, ABCL)
If there is a signal which would inhibit the strike-in of a AHBC then the default is that it is that the train is assumed to be stopping unless the signaller selects Non-stopping, Therefore normal aspect is red (note the very latest NR standard does not depict the normal aspect of a signal with a double bar but I think the IRSE examiners still expect you to show like that!)
AOCLs are almost always provided on lines with little lineside signalling and the crossing speed will be low so the strike-in short. Hence the situation wouldn't arise- just wouldn't want a colourlight signal very close to a crossing that would appear to be protecting it but actually wasn't- contradictory messages to the driver. I can think of one place where this rule is broken, though it is not on NR but a private railway. As I understand it the local council wanted a new road to cross the tourist railway and were funding the crossing and dictated what they would pay for. I think it ended up as an ABCL and because it was close to the terminal station there had to be a signal at the position just prior to the crossing. The result was a 3 aspect signal with the lowest one being red, the middle one being the "Drivers White Light" and the top being the yellow. I am sure that there is interlocking between the DWL and the proceed aspect but I can't remember all the details- I think that the signal goes to yellow first but the driver also needs the white light to proceed. Couldn't get away with this on NR but since the rest of the railway uses historic semaphore signalling there is no risk of driver confusion and hence the unique solution.
Quote:#4 If a signal is placed inside a tunnel, what precautionary measure we have to adopt?
a) Best not to have one there, if can be avoided.
b)If have to have one, try to ensure not encountered at danger more than it has to be ( tunnel controls )
c) Recognise that it may have to be ground mounted with the red at the top, or perhaps a miniature one mounted on tunnel wall. Certainly not going to be room for PLJI and SARI- sometimes there has to be dispensation to permit use of MARI.
d) Think about the driver's safety if they need to contact signaller by SPT- a wall mounted phone with long lead so that driver can reach out and then converse in safety of their cab for example.
For the exam just show that you have considered such issues but have selected that position as the "least bad" option
Quote:#5 Please explain the logic behind MAY-YY in 4 aspect signalling.Have you read section S9 of the Study Pack?
I feel that explains it but if you feel otherwise than ask a specific question.
I don't recommend using it in the IRSE exam as not very common and you'd need to do some calculations to justify use, that would take valuable time.
[quote]
#6 When the speed difference between main line and divergence is 33% can we go for MAY