Re: It's still academic

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

MattyQ wrote:

> >What about Yellow over Yellow:
> >
> >NSW: - diverge, next sig at caution?
> >VIC: - 3 pos repeater, nest sig at stop
> >QLD: - next sig at Single yellow, dunno the proper name of the aspect
> 
> YES !!!! We have a winner !!!

No you don't - not quite. NSW yellow over yellow does NOT mean diverge,
next signal at caution. It just means diverge, next signal AT LEAST AT
caution or showing yet another turnout indication. Yellow over yellow is
the most unrestrictive indication obtainable for a turnout, so even if
the next signal is at full clear, you can't get anything "clearer" than
yellow over yellow.

Various reasons have been suggested for the lack of yellow over green as
the "natural" aspect in the last-mentioned situation, but the people who
would definitively know are long since unavailable. The most popular
theories are (a) they didn't want to create an inversion situation where
someone might thoughtlessly interpret yellow over green as meaning green
over yellow and (b) they didn't want to downgrade the immediate impact
of the top yellow by having a green on view as well.

Moreover the definition above of the Victorian yellow over yellow is not
right either, but I'll leave the Victorians to comment on that. [Hint:
note the new repeaters on the standard gauge.]

Eddie Oliver