Re: Concord derailment

[Eddie.Oliver@efs.mq.edu.au (Eddie Oliver)]

markbau1@aol.com (MarkBau1) wrote:

>Yes but even NORAC rule 287 says you WILL BE DIVERGING, although I only
>operated under NORAC rules for a short while I know that the bottom light did
>mean you were diverging.

If the top light was red, yes, but not necessarily if the top light was yellow. Depends
on which railroad, because even NORAC did not completely standardise across
roads (it couldn't when, for instance, there are still plenty of Pennsylvania position
light signals and the colourised derivatives thereof.)

> Yes it gives a max. speed, like GCOR does, but the
>important thing is that it tells you that you are diverging, unlike speed
>signalling where the signals merely tell you what speed to go and give no clue
>to wheather you are diverging.

That, with respect, is not quite the point.

It is true that in Melbourne red over yellow may or may not have a diverging
implication, and this ambiguity  is perhaps unique. But the US aspect relevant to this
discussion is yellow over green, i.e. approach medium in NORAC and directly
analogous to the "medium" green over yellow indication in NSW.

Some NORAC roads and their predecessors have/had a concept of
"advance approach" which was different from approach medium, so that
the latter could therefore mean (in effect) approach diverging.  However
others use/used approach medium to mean BOTH advance approach
and approach diverging, which was logical to them because a signal
at approach had to be passed only at medium speed anyway.

Roads in this latter category thus have exactly the same ambiguity
as exists in NSW green over yellow.

[For Australian readers not accustomed to American terminology, I should
perhaps explain that American terminology is to use "approach"
(as a word on its own) as the name for what in NSW would be called
 "caution" or in Victoria "normal speed warning".  However the word
 "approach" if preceding another word is an instruction of what to do
at the NEXT signal, so "approach medium" = NSW "medium" =
Victorian "reduce to medium speed".  Some roads even have
compounds like "medium approach slow", i.e. pass this signal
at medium speed and be prepared to pass the next signal at
slow speed.]

Eddie Oliver