signal questions 3

[NW Mailing List]

Jim,

> http://www.railpictures.net/viewphoto.php?id=472679

Jimmy's answers are correct, but some additional details to place them
in context with the phots might help.

First, in case it isn't obvious, the light source backlighting the signals
and electrical cabinet in the above-linked photo is NOT a train but a
'street light' style security light for a residence.

Second, yes the view is looking (timetable) east. However, the eastbound
signals are NOT a control point just because of the single lights on the
bottom target. The Ingleside signals are automatics in both directions.
The next signal to the east is also an automatic, so there is no need
for additional lights on the bottom target since this signal does not
have a need to display any diverging or advance approach aspects. The
next signal to the west is the control point of Blake, so the westbound
signals need more lights on the bottom target for diverging indications.

In this photo, there is an eastbound movement lined on the near track
(main 1), hence the red signal for that track on the westbound signal.
The main 2 aspects in both directions are the normal aspects with no
signals lined for movement on that track at either Blake (next control
point to west) or Oakvale (next control point to east). See this photo
for an example of both mains exhibiting this behavior, with no trains
lined on either track:
http://www.railpictures.net/viewphoto.php?id=504580
(the light to the left of the signals is the light source in the first
picture). Since the next signals to the west is a control point, the
default indication for the westbound signals is approach, while the 
default indication for the eastbound signals is clear since the next
signal to the east is another automatic. When no train is lined, the
signals default to the most favorable indication possible as defined
by normal automatic block signals rules. 

At the risk of confusing things even more, note that there is no milepost
marker displayed on the eastbound signal. That means that this automatic
signal is unlike most other automatics in that it displays (eastbound
only) a 'stop and stay' indication instead of a 'stop and proceed'
indication, presumably due to the grade and curves here. The lack of
milepost markers on the signal does not make it a control point (well,
not a dispatcher-controled CTC control point, anyway). Real railroaders,
help me out here - is there a better term for this than 'stop and stay
automatic'?


> http://www.railpictures.net/viewphoto.php?id=510649

The Willowton photo demonstrates the same logic as explained by Jimmy.
In this timetable west view, the near track (main 2) has an eastbound
train lined (and coming just around the corner) hence the red signal on
the right, while no train is lined on the far track at either control
point to the east or west, so both eastbound and westbound main 1
signals are showing their default approach indications. In this case,
the default is approach because the next signal in both directions is
a control point.

Just a much more verbose version of what Jimmy said...

Joe Shaw
Christiansburg, VA
http://www.krunk.org/