Interesting signals

Well, to me at least, because they're not very common, and they were both in Portland. Leaving the main line on the train, and diverging to the branch to the passenger station, we got a red-over-red-over-green [slow clear, I think]. Coming out of the station, the approach signal was yellow-over-yellow [ don;t know what that's called].

I think Yellow over Yellow is an indcation to let the engineer know to
be prepared to stop at next signal unless the train infrount of him/her has cleared.

I was curious so I looked up the NORAC rules which Pan Am follows, I think.
Yellow-over-yellow is an "approach slow", which requires an immediate reduction to to medium speed, and approach the next signal at Slow Speed. I don't ever remember seeing these on the B&M.

Rockingham, you are correct about both. Red over Red over Green is a Slow Clear and the Yellow over Yellow is an Approach Slow, which usually means the move will be making a diverging move at the next signal which will be at Slow Speed.

New York Central, then later Metro North, had the double yellow both on intermediates, and on three-head interlockings. It was an "advance approach", I think. In any case, it was the aspect on a signal when the second signal ahead was "stop".

I'm wondering where else on Pan Am an engineer has the possibility of seeing a slow clear.