Re: Signalling Questions in Brisbane?

[Eddie Oliver <eoliver@efs.mq.edu.au>]

signal_spotter@my-deja.com wrote:

> QR taken 99% of the British system and added the complexity of point
> sequencing to it ie putting the home signals right on the points (ala
> NSW practice) therefore requiring the overlap to be proved before
> swinging it. In UK they put the homes back about 185m from the points
> to minimise this.

I don't know, but here are a few obvious theories - perhaps you can come
up with some more:

1. QR and NSW tend to have closer signal spacing than Britain, so that
having the homes a long way back from the points is inconsistent with
the general spacing patterns. For instance: Even close to the London
termini, signals are often something like 700 metres apart, so 185
metres is pretty trivial in comparison - but we might have five signals
in the 700 metres and at least two in the 185.

2. Another British affliction was insistence that once a signal has been
cleared, overlaps should not be modified - so it was an extraordinary
change of approach for them even to consider swinging overlaps at all,
and hence when they made that concession, they did their best to
minimise its perceived "threats".

3. QR and NSW simply don't want the time wastage resulting from trains
standing further back from junctions than is really necessary.

Eddie