Re: New questions for rail experts

[Chris Gordon <cmgord@alphalink.com.au>]

> OK to answer everyones queries about trainstops, catch points I'll
> explain it in technical detail. Guards Indicators have been pretty well
> explained by the others so I won't elaborate.
> 
> Trainstops. The arm that you see raise and lower is a trainstop. When
> the signal is at red it is raised. When the aspect is cleared ie
> yellow, green etc it lowers straight away. Normally subsidiary shunts
> don't drive the trainstops unless it's a specific passenger move under
> a shunt signal. Not that normal but there are a few cases say at
> Hornsby. Also if the signal is capable of showing a low speed aspect
> then the lowering of the trainstop is acheived after proving the
> approach speed of the train at 35kph. They are positioned at all
> mainline signals (not ground shunts) to stop a train (ones fitted with
> trip cocks) if it passes the signal at stop. There is also a
> requirement for Intermediate Trainstops if there is little or no
> overlap (the margin of error worked out using trip braking curves based
> on the linespeed) after the next signal. These are what you may be
> referring to every 50 m or so. They are positioned to prove the train
> at 35kph, then 25kph and then 10kph. The latter 2 required if the
> overlap is <100m. To answer another postee's gripe about catchpoints,
> we are currently putting in Intermediate Trainstops throughout Sydney
> on routes leading up to catchpoints. I personally have designed
> Coalcliff, Scarborough, Dapto (that's not a CP but for another reason)
> and a few others. Anyway what we hope to acheive is that for signals
> reading up to open catchpoints the signal in the rear will display a
> low speed (with a timed approach) and when the train has been proven at
> 35kph it's then tracked through the route (at 25kph and 10kph) dropping
> the ITS's as he goes. What that means is that by the time he reaches
> the end signal (that's at stop) and with an open catch his speed will
> have been proven that if he does trip past it, it will be at a low
> enough speed (10 kph) that he will not progress through and derail. If
> his speed exceeds then he will trip on an ITS prior to the stop signal.
> 
> Anyway hope this explains trainstops.

Thanks you very much.

If you have enough train stops, overlap, and prove the train is going
slower than the correct speed (as outline above, and Melbourne has
something Similar in the City Loop, at Kooyong, Gardner for the
tram/train level crossings, Ringwood, Heidelberg, Cheltenham, and maybe
a few others) then there is no need for catch points on the main line.

Of course if the driver is doing more that the speed limit of that
section of track then the overlaps, and train stops will not be enough
to stop a train going through a red signal in time (unless there is
speed proving train stops, which trip the train earlier)

There is a safety factor built in, but track sections like the up and
down lines (not center line between Burnley and Box Hill which is 85
km/h) between Richmond and Blackburn have a restriction of 65km/h, it is
quite easy for the driver to be speeding along this track.  


-- 

Chris Gordon

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