Posted by: "cv_acr"cv_acr@xxxxxxxxx cv_acr
Date: Thu Oct 4, 2012 9:28 am ((PDT))
>Thus in the early 60's a lot of ABS signals became absolute. These aren't ONLYAll true of course in the rules (and Vic is the undisputed expert in the rules, having lots of
identified by the "A" markers either, but can also be by two signal heads NOT
staggered in relation to each other, and of course, three headed signals except where PL
(Position Light) and CPL (Colour Position Light) signals were used -- none in Canada, nor on
CP Lines in the US inter alia.
>
firsthand experience!) although in practice I've only ever seen multi-headed "absolute"
signals in CTC or interlockings, and only ever seen a single-headed signal with an "A"
plate at sidings in ABS.
So (in Canadian practice):
Single-head signal with "A" plate reserved for ABS/APB
Multi-head signal (non-staggered) reserved for interlockings/CTC control points.
Technically the rulebook could allow either type to be used, but what I've seen
so far has always been consistent.
(Someone will probably now hit me with an example of an exception, but that's a
good general rule of thumb.)
Triple head signals of course allow for medium and limited speeds, and found at
[controlled] crossovers and interlockings with high speed switches.
