Re: Double Colour Light Signalling

["Hairbear" <prize5@s054.aone.net.au>]

Michael Cuthbert wrote in message
<34CAD98A.5D01@sydney.nospam.dialix.oz.au>...
>
>Three things:
>1) It strikes me as a little odd that a 25km/h turnout has the same
>indication as a 80 km/h turnout. The second often doesn't even need a
>speed reduction, while the first does. Maybe a new indication (say,
>Yellow on Green) could be used for the high speed turnouts.
>
>2) The turnout for the Down Track at Epping (NSW, if you didn't guess)
>doesn't have a turnout indication! Instead it has 'standard' signalling,
>with green/green indicating clear track and the driver is just meant to
>know.
>
>3) North Shore Line (NSW) signalling. I've noticed that some of the
>signals are missing the "caution" aspect (Green/Yellow), instead
>progressing from R/R, G/R, G/G. Why is this so on a pretty heavily used
>track? An anti-blocking measure?
>
>Mike Cuthbert.
>

1) The turnout indication is more to let the driver know where the route is
set, as opposed to the speed through the turnout, the driver should know the
speed through all turnouts he or she travels over. There has been a "new"
(for NSW) indication introduced in recent years at Cabramatta and Merrylands
(these locations have higher speed turnouts installed), where the driver
gets a "normal" indication e.g. G/Y or G/G with a band of white lights above
the signal to indicate which direction the route is set.

2)  A turnout indication is not required at Epping (I'm assuming you mean
the signals at the northern end of Epping) as there are two roads converging
to one, therefore there is only one way you can go, hence G/G indication
from either down main or middle road.

3)  I am not familiar with the North Shore Line but the signalling set up
you mentioned is in practice in other areas.  From my observations the
missing "medium" indication(Green over Yellow) is in place where colour
light signalling was installed many years ago when traffic density was much
less and has not been updated since. In this age of larger and heavier
freight trains in is certainly preferable, from a divers point of view, to
have the "medium" indication in place as it gives the driver one block more
warning of a signal at stop.


Bear