Roanoke Junction - NELSON'S CROSSOVER

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My understanding is that the 'old main line' (east) end of the Nelson
Crossover is electrically locked, since it is inside of the Park Street
control point. The west end of the crossover on the Forwarding Yard
ladder is outside of the control point, so can be a simple hand-throw
crossover.

In Ron Davis's photograph of the non-so-new derail by the VMT,
http://nwhs.org/wiki/show_image.php?id=570 ,
the track closest to the VMT is the "Old Main Line". The derail is a
dispatcher controled powered derail, protected by a signal behind
the photographer. The crossover switch beyond the derail appears to
be electrically locked. Notice that it does not have the simple
green/yellow target stand like the switch for the west (near) end of
the crossover. The dwarf signal on the crossover protect movements
into the interlocking.

I was under the impression that the dwarf was a dispatcher controlled
signal, but based on Mr. Sander's comments I may be incorrect on that,
Most other instances of electrically locked switches I know about do
not have signals on the associated track, so this setup is rare.

The next track to the left is the Forwarding Yard ladder. The switch
machine visible in the foreground is for a just out of sight power
switch to track 6. The first visible turnout is the hand throw
switch for the west end of the crossover. Note that does not have a
large flat black box like the forward switch machine.  The second
visible turnout is the power switch that leads to the (sub-)ladder
for forwarding yard tracks 7, 8 and 9.  On that sub-ladder is visible
a power switch for track 7 (the closest route).

At the far end of the Forwarding Yard ladder track at the very top of
the picture is a crossover between the ladder and the second track from
the left. (Is that track considered main 1 at this point? )  The track
on the farthest left is Main 2.  Out of sight off the top of the photo
are two signals for the Forwarding Yard Ladder track and the maybe-main-1
track that govern movement east off those tracking into the Park Street
control point. The visible portion of main 2 is already part of the
control point. The visible sections of the maybe-main-1 and forwarding
yard ladder are NOT part of an interlocking.

So, Mr. Burnett, your understanding is not so far off from reality.
Only certains tracks in the photo are technically part of an
interlocking.

My confusion is the polar opposite of Mr Burnett's. How can you have
dispatcher controlled power switches outside the interlocking (control
point)?  It seems counterintuitive to me, but they exist in Roanoke,
Bluefield, and Williamson at least, and probably elsewhere. I presume
there are timetable instructions governing movement through them, and
those instructions probably require permission from the yardmaster to
foul the switches. I guess it's just cheaper (and less complex) than
having a seperate signal for every yard track.


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