Re: Derailments on the CityRail Network

[signal_spotter@my-deja.com]

In article <3992b7c6@news.rivernet.com.au>,
  "Jeff Melvaine" <jeffm52@rivernet.com.au> wrote:
>
> Glen O'Riley wrote in message <398b9a37@pink.one.net.au>...
> >Well explain catch points, my assumption is that they switch when a
train
> is
> >in the wrong place at the wrong time and derail it.
> >
> They don't switch because a train comes along at the wrong time/place.
> Their normal position (i.e. when signals are at stop) is open (i.e. a
train
> running through them will go off into the dirt).  When there is
nothing in
> conflict with the route they protect, they can be closed, and then the
> signal for that route can be cleared.  Then they must be put back to
the
> open position before any signal can be cleared for a conflicting
route.
>
>
But generally the conflicting route is one that requires the
catchpoints closed as well, just from the opposite direction. What you
probably meant to say was that catchpoints protect flank routes.
Consider 2 lines running parallel and they join at one end via a set of
points and there is a signal protecting each end of the line. Now you
could not set routes up to both signals because their overlaps would
conflict. However if you put a set of catchpoints in one of the lines
(it will operate in conjunction with the main points) then you can set
routes up to both signals as both routes will have valid overlaps, one
overlap along the track and the other overlap through the catchpoints
open. Now this is the dilemma. Trains are passing these signals at
danger and derailing through these catchpoints so we are putting
Intermediate Trainstops leading up to signals at catchpoints to track a
trains speed through the route and trip it early if it's going to fast
and likely to career through the open catchpoints.

regards Ian
Signal Design Engineer


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