Re: Signalling in Victoria

[Eddie Oliver <eoliver@efs.mq.edu.au>]

MarkBau1 wrote:

> 
> This is debatable. Many, including signal Engineers, define speed signalling as
> an additional proceed aspect behind a train,
> G/R Y/G R/Y R/R
> instead of
> G/R Y/R R/R

Can you please identify some of these "many" people? Are they
exclusively in Victoria, because I don't know of any anywhere else in
the world?

The distinction between "speed signalling" and "route signalling" is
surely practically universal in the standard signalling literature, even
though there are always going to be cases for which either or neither
description may reasonably apply (e.g. Victorian 3 position signalling
is clearly speed signalling but is sometimes accompanied by specific, as
distinct from implied, route information).

Mark has said on various occasions that in his interpretation, 

> OTOH, it is true that NOW VR 3 pos signalling only tells you speed and not
> route (hence the need for route indicators at some locations) like it did when
> introduced.
> 
> Many people refer to Essendon to Newmarket as the introduction of speed
> signalling as this was the first time a bottom light/arm did not mean you were
> diverging and the rules were changed to reflect this new use of the bottom
> light/arm.

Perhaps the people in possession of early Victorian rulebooks can cast
some specific light on this. However I suspect that the supposed
"change" was simply circumstantial rather than a genuine change: i.e.
originally the only medium speed routes were divergences, and therefore
the two interpretations were logically equivalent anyway; but when
medium speed non-diverging routes were established, someone had to make
up their mind as to a definitive one or the other. In other words, if a
particular system can equally well be interpreted as BOTH speed and
route signalling, it is academic which you call it; you only need to
make the distinction when an indication is displayed that has a meaning
in one system type but not in the other, or would have different
meanings in the two systems.

This also casts some light on Mark's statement that the four-aspect
signalling was referred to by some people as the "real" speed
signalling: I submit that this association is simply because the
four-aspect signals were the first ones for which the distinction
between route and speed signalling had any specific effect in Victoria.

Specifically, the introduction of reduce to medium speed as an advance
warning, followed by medium speed warning as the indication immediately
prior to the signal at stop, imposed the medium speed situation on
straight track with no divergences at all. Thus this was the first time
that anyone had to THINK of the aspects purely in speed rather than
divergence terms.

Eddie Oliver