Re: Derailment at Concort West - Reason

[alberta@zip.com.au (Albert Alcoceba)]

On Wed, 10 Jun 1998 19:28:28 +1000, Wollongong Quokka
<quokka@zipper.zip.com.au> wrote:

> 
>> 
>>            o
>>             o
>>              o           |B|
>> G            G            G  [tn'out]  G
>> G   ----->   G   ----->   G   ----->   G
>> 
>> 
>> Whilst I'm not sure of the signalling arrangement at Concord, it seems that
>> confusion over the meaning of signals may have been a contributing factor. The
>> above arrangement would help reduce such confusion.
>
>A variation on this theme appears to be fairly common on the South Coast
>line, with the use of a fairly obvious indication of a turnout.  Is there
>any reason why this appears to be the case here and not elsewhere?

That slanted set of white lights is always used for turnouts on single
light colour light signalled areas (ie. 1 main light on each signal
post).  Generally this is in place outside the Sydney Suburban area.

It is unusual in Double Light Colour Light areas like most of the
Suburban area.

The reason is that in single light areas, you can only show Red
(Stop), Yellow (Slow) or Green (Clear).  Some areas do use Pulsating
Yellow as a Medium indication.  There are no indications left to show
a turnout.  With double lights you can use Yellow/Yellow and
Yellow/Red for turnouts.



Albert Alcoceba
alberta@zip.com.au
http://www.zip.com.au/~alberta