Re: [NSW] Olympic Park/City Railway Signalling Question

[David Johnson <trainman@ozemail.com.au>]

Chris Downs wrote:

> One of the operational limitations at Olympic Park was the delay between a
> service departing either platforms 1/2 or 3/4 and the following train
> entering the same platform.  It appears that the signal permitting entry to
> the platform did not clear to caution until the preceding train had cleared
> the tunnel portal or thereabouts some 200m beyond the station.  The
> practical implication of this was that even when trains were queued it was
> about 90 seconds usual minimum from the 1st train starting until the 2nd
> train stopped, quite a chunk out of 4 minute headways.
>
> When reading David R. Keenan's and Howard R. Clark's "FIRST STOP CENTRAL"
> they refer to the later version of speed control signalling used in most of
> the City Railway (except the St James - Central leg which uses the earlier
> version).  The following statement is made (page 67):
> "At peak periods it is possible for a following train to closely approach a
> station while the previous train is still in the platform.  In some cases
> when this close headway is in operation, the platform entering signal can
> clear before a preceding train is completely out of the station in order to
> allow the entry of the following train without delay."

I also have a question.  What was the signal indication given?  If it was giving
a low speed indication (Red over Red over Green), and there was a train between
that signal and the next, it would be a signal irregularity.  The only possible
indication would be a calling on signal (Red over Red over CO), but the signals
before the platforms are all automatics, and Calling On signals must be fitted
to Home signals (and variations thereof).  Also, a Calling On signal is supposed
to have the trip up, which defeats the purpose of clearing it.  Does anyone know
the full details?

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