signal aspect

NW Mailing List nw-mailing-list at
Wed Nov 26 16:59:34 EST 2014

Jim Cochran asked:
> If a Westbound is preparing to depart Bluefield on main 1 and the crossover
> turnout is set for him to crossover to main 2 and the next turnout is set
> for him to head down the Clinch valley, what aspect will he see at that
> funky signal that has both a cantilever for main 2 and a single mast for
> main 1?  Will it show Diverging Approach Diverging?

I believe the signal would show Stop (and stay), because I don't think that
is a realistic route. Hopefully one one our signal maintainer members will
correct me if I'm wrong, but I don't think the field signal hardware would
actually allow a route to be lined through the control point if both
crossovers between double track mains are both reversed, even if it is a
'physically possbile' route. Even if it was, it would not show Diverging
Approach Diverging for that case, since all the turnouts/switches/crossovers
are included within a single control point, and Diverging Approach Diverging
means you are diverging at both this and the next control point.

For the westbound signals at Bluefield VA, the cantilever is for main 1,
the single mast is for main 2. Whether the westbound train is approaching
on main 1 or main 2, the respective signal will display the same indication
to a train routed to the Clinch Valley:
Diverging Apporach: If not lined at Graham (Graham showing Stop).
Diverging Clear: If lined main to main at Graham (Graham showing Clear or Approach).
Diverging Approach Diverging: If lined main to siding at Graham (Graham showing Diverging Approach)

In other words, it doesn't matter how many switches you are diverging through
at a single control point, you won't get a Diverging Approach Diverging unless
you will be diverging at the NEXT control point as well (and not leaving CTC
before you get there).

Joe Shaw
Christiansburg, VA

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