Re: Crossing loop design (r.e. Southern Aurora crash)

["MattyQ" <matticue@corplink.com.au>]

MarkBau1 wrote in message <19990222033341.00954.00001465@ng-fb1.aol.com>...
>This is analogous to the US system where there are either "absolutes" or
>"permissives"
>
>Identification of them is acheived by the signal having or not having
number
>plates.
>
>IE, Absolutes do not have a number plate, permisives do have number plates.


Mark,
            In NSW, Vic and SA, automatic (or permissive if you live in SA)
signals are identified by staggered signal heads. NSW has a strict rule -
lower light must be 200mm to the right of the upper light. This rule does
not apply in Victoria. Signal heads can be staggered left or right and can
have different spacings between the upper and lower head.

Good example is two auto's at Hoppers Crossing. Down signals on gantry,
signal on West line has lower head staggered to right about 4 feet below
upper head. Adjacent East line signal has lower head staggered to left and
about 7 feet below upper head. I'm told this is due to signal sighting
difficulties associated with overhead wiring.

I don't know what rules apply in SA, however, I have never seen an SA signal
staggered to the left. I was once told that the new AAR code of practice is
not to stagger signal heads. Is this correct?

Regards

Matt Smith
Brisbane, Queensland
Reply to matticue@hotmail.com

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