Another basic signalling question - how does bi-di work in terms of signal aspects? I'm heading south from Edinburgh and noticed that on the approach to Grantshouse the bi-di signalling had a conventional G-YY-Y-R sequence.
So how does this tie in with the right-road signals to avoid a green in both directions at the same time? Is it (pardon the crude ASCII art):
G->YY->Y->R-R<-Y<-YY<-G (i.e. red at either end of a single block section) or:
G->YY->Y->R-R-R<-Y-<-YY<-G (i.e. an 'empty' section between the two reds)?
So how does this tie in with the right-road signals to avoid a green in both directions at the same time? Is it (pardon the crude ASCII art):
G->YY->Y->R-R<-Y<-YY<-G (i.e. red at either end of a single block section) or:
G->YY->Y->R-R-R<-Y-<-YY<-G (i.e. an 'empty' section between the two reds)?