Re: Overlap block system traffic
- From: "cv_acr" <cv_acr@xxxxxxxxx>
- To: cpsig@xxxxxxxxxxxxxxx
- Date: Thu, 04 Oct 2012 16:28:36 -0000
Thus in the early 60's a lot of ABS signals became absolute. These aren't
ONLY 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.
All true of course in the rules (and Vic is the undisputed expert in the rules,
having lots of 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.
Chris vanderHeide
Sarnia, ON
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