Norfolk Southern Signals

[cec209]

Does anyone have insight on Norfolk Southern's use of cantilever signal towers versus single masts for signals. In other words when is a cantilever used instead of a single mast and vice versus?
Thanks,
Charlie

[cv_acr]

Not specific to NS but...

A single mast applies to the track it's located next to. Usually located to the right of the track, although it has become more common to place a signal to the left of the left-most track if that's the track it controls. Otherwise it MUST be right of the track so there is no confusion.

e.g. the Canadian UCOR had this rule:

246. Whenever practicable, train order signals will be located adjacent to the train order office to which they apply, and other fixed signals, except switches, will be located to the right of the track which they govern. Where conditions require other locations they will indicated in special instructions.

If you have a track in between other tracks, the signal must be to the right of that track. This requires a bridge or cantilever structure, or dummy arm to locate the signal properly and denote which track it applies to.

[cv_acr]

Signal structure drawings:

[nickelplate759]

Wow!  I always wondered why there were dummy arms.

[draskouasshat]

it all comes down to sight distance and obstacles. if theres a tight curve, highway bridge, hills(a train coming up a hill and yes, youd be surprised about the hills a main line climbs that will block views) or anything that might impede the view of an approaching train from seeing the signal,  the other major reason for a bridge or cantilever signal is due to track layout and the room to actually put in a stand alone mast signal. if theres a track on each side the track that said signal is governing and theres no room, we will install a bridge or cant.

Drasko