(11-03-2010, 10:03 PM)interesting_signal Wrote: j) what I actually meant was "how does the MEANING of the aspect differ to the driver"
The meaning is the same to the driver. 144 is only an independent shunt signal because there is no main signal at this point.
Does that answer the question?
m) Thanks for the explanation. That makes sense now. Yes, I didn't really know how to find the foul tracks for the points, or how to tell whether the joint was beyond the clearance point or not.
I'm in the middle of updating the control tables, and am trying 211 points too.
Thanks for your help!
A PL aspect means "proceed as far as the line is clear"; i.e. this is a promise to the driver that "the points are set and locked appropriately and that there is nothing coming towards you or will come in from the side- however there may be a train anywhere in front of you (either stationary or going in the same direction) and you must be able to stop before hitting it".
The difference is that when the PL is associated with a main aspect and when routed to a line which is defined to be "passenger permissive", (generally platforms at some major stations) then you may enter the occupied line with a passenger train. A GPL is only ever a shunting signal, not authorised by use by passenger trains and if routed into sidings, can only be taken as proving infrastructure on the runnning line (i.e. there could be points set incorrectly or opposing shunting movements taking place at low speed within the confines of the yard / siding. Sometimes it may prove more (e.g. the first set of handpoints, an aopposing move or perhaps even train detection is there is any); when doing a CT one should generally include in the aspect as much as is possible without preventing the signal showing proceed in circumstances when this may be required for an operational move that is needed.
PJW