[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Double Colour Light Signalling



Michael Cuthbert wrote:

> 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.

Why?  The driver knows where every speed board is in the metropolitan area.  He
also knows the turnout speeds.  The only information that he doesn't know, is
whether he is going straight, or taking the turnout, and this information is
relayed via the signal.  The new turnouts at Cabramatta doesn't even have a
turnout (Y/Y) indication.  It is indicated with normal Green over Red/Yellow/Green
indications, and a route indicator.

> 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.

That's right.  The driver just knows.  All he needs to know is whether he can go
or not.  He knows what the track speed is on each line.

> 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?
>

This is the "medium" aspect.  The reason it is omitted is because at track speed,
there is enough distance from a green over red indication to stop before the red
over red indication.  The medium aspect is only required where signals are too
close together, and the line speed is too high to allow a train travelling at
track speed to stop on one signal's notice.

--
David Johnson
CityRail Guard
trainman@ozemail.com.au
http://www.ozemail.com.au/~trainman/