(05-12-2009, 10:11 PM)Peter Wrote:(05-12-2009, 01:26 PM)MarkN Wrote:(22-09-2009, 09:58 AM)Peter Wrote: For 10 and 12 signals, you have given them SIs rather than PLJIs. Although these are MAR for the turnout route, I would normally expect them to be PLJIs for such a signal. Conversely, 7 and 157 have PLJI for all routes. This is a problem for the route into the bay as this is not allowed.
Could you give a reference for the use of PLJI into a bay? I have looked through the group standards GK/RT 0031 and 0032 and cant find one. I would normally place an SI here as custom and practice but did not know that the use of PLJI into a bay was outlawed.
Thanks
Very good point. I cannot find it in the standards, but it is something that stuck in my mind from IST or the like, but now I have come to look for it..... I'll check with some older and wiser people and come back to you.
It is something that has come in relatively recently with NR's insturction NR/L2/SIG/19609. This states in section 6.1:
A PLJI shall be used in association with main aspects where more than one route exists except where an SI is required due to one of the following conditions:-
a) The route destination is a terminal platform. In cases where there are no through routes from the junction signal an indication shall be provided for all routes.
b) etc
You will find that there are plenty of places where there is a PLJI into a bay and I don't see any particular problem with it. I suppose the argument is that it is unlikely that the turnout will be particularly fast and in a multi parallel line to multiple platforms at a through station it can be confusing to the driver that the bay platform could be a PLJI pos1 on one line, PLJI pos2 from the adjacent line and PLJI pos3 from the next.
Flasshing aspects to a PLJI into a bay platform was always banned (but certainly High Wycombe did feature this on the TOC's insistence when MAS was installed in the early 1990s- I wouldn't be completely suprised to find that it is still like that- since the line has ATP then I suppose that any risk is mitigated.
Be aware that some signalling "rules" change; partly it is "preferential engineering", partly because an incident has occurred, sometimes the environment changes or is different locally to nationally. As far as I know a PLJI into a terminal platform would not require a non-compliance to a Railway Group Standard (i.e. such an indication is compatible with the Rule Book etc); however it isn't good practice to provide one.
PJW