Re: Concord West - Availability of Accident Report

[craigd@lios.apana.org.au (C. Dewick)]

In <zXUo3.14$VE1.2596@nsw.nnrp.telstra.net> "Chris Downs" <cvdowns@hermes.net.au> writes:

>Does anyone know:

>a)    Is the Concord West accident report publicly available?

It has been released, but you'd probably have to pay the NSW government body
that sells copies of government documents, etc. to get one.

>I'm curious as to whether or not any consideration was given to the
>ambiguous nature of Green over Yellow indications.

>For those unfamiliar with NSW suburban signalling in the Concord West area,
>on a straight line run (ie no turnouts) from an all clear signal to one at
>danger the consecutive signal aspects are:

>Green over Green
>Green over Yellow
>Green over Red
>Red over Red over Green (trip raised and lowers on a time release)
>Red over Red.

>When approaching a turnout the usual conseutive signal aspects from all
>clear are:

>Green over Green
>Green over Yellow
>Yellow over Yellow (turnout indication - also all clear).

>I appears that the situation at Concord West was/is:

>Green over Green
>Green over Yellow
>Green over Yellow (again, ie repeated))
>Yellow over Yellow.

That's how it is supposed to be, but the issue was whether or not that's
what the driver saw. If he only saw one signal displaying medium caution
(green over yellow) he could have presumed the next signal would be at least
main line caution (green over red), or another medium caution, not turnout
(yellow over yellow, or yellow over red).

I'm not qualified for working a train on the down relief road in the up
direction, so I can't comment on whether trains turning out off the up main
see two medium cautions before the home/starter that protects the high-speed
turnout over on the down main.

It's not actually part of the signalling rules that there have to be two
medium cautions - it's done simply because the safe braking distances are
not enough for a heavy freight train travelling at full speed (115 kmh) is
not enough to slow down to a safe speed (depending on where the train is
going to) once the driver sights a medium caution signal. If, in the case of
Concord west and the *up* relief line, there is no way that only one medium
caution is enough before the home signal protecting the 25 kmh turnout into
the up relief line.

The down relief has 80 kmh high-speed turnouts at Concord West, and the
signal protecting them on the up main is two signals back from the one that
protects the start of the up relief.

>This is a fast section of track (115km/h for suburbans). 

And also for most 'high wheeler' freight trains (except they'd all be
slowing down to at least 80 kmh to get onto the down relief)

Regards,

Craig.
-- 
            Craig Ian Dewick            |       Stand clear - jaws closing
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