signal questions 3

[NW Mailing List]

At first glance,
http://www.railpictures.net/viewphoto.php?id=472679&nseq=319 looks like a
recipe for disaster at Ingleside. But what is really going on here? I
believe the camera is looking into the aspects that an Eastbound movement
would observe and it shows clear for both mains. Because of the long
exposure, we can also see reflections of the Westbound aspects, and they
are stop and ?approach? Why would you ever want opposing movements to both
see “go ahead” aspects for the same track at the same point? Let's dig a
little deeper. The Eastbound signals are a control point (note the single
lights under the top arm) for the next block. However, the Westbound
signals are intermediates (automatic). It appears that the dispatcher has
set routes Eastward on both mains, thus the clear aspects. One of the
Westbound intermediates is showing stop and proceed, as I would have
expected, but why does the other show approach? Under the “tumble down”
operational scenario, I was under the impression that when a route was
established between control points for a movement in one direction, all the
intermediates between the two control points were immediately dropped to
their most resticting aspect, i.e. stop and proceed. My question is: why
does the one intermediate show approach, and why is this safe? Another
example of this seemingly unsafe behaviour is shown in
http://www.railpictures.net/viewphoto.php?id=510649&nseq=1 at Willowton.

Thanks, Jim Cochran
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