PGentieu posted:I can understand the 3-over-2, since the cycle tended to be "Clear(green over red) , Stop(red over red), Approach(yellow over red), Approach Medium (yellow over green), Clear (green over red again)" as the train progressed through each succeeding block.
So where would the second yellow come into play? I thought maybe if the signals were close enough together a second yellow might be needed to show "Advance Approach (yellow over yellow)", but that by itself doesn't explain why a second green would also be needed on the lower head.
I'm not familiar with CNJ signaling, but from your wording about a second green or second yellow I get the impression you may have a misconception about how signal heads are normally used. That is, a single signal head does not show more than one light; in other words, green over red or any other combination would not be shown on one head. The top head would show one color and the bottom head would show the other. So, a "second green" is needed because if the top head is displaying yellow, then the bottom head has to display the green for yellow over green.
Also, railroad signals typically have vertical color light signals arranged the opposite way from highway traffic lights - that is, railroad signals typically have green at the top and red at the bottom.
The misconception seems to be what I meant by a block signal, and yes, on most railroads automatic block signals had only one head. This was not the case for the CNJ. On the New York and Long Branch particularly, block signals had two heads. The lower one was mounted on the opposite side of the pole from the upper head. Red was indeed always on the bottom light of each head and green on top, and the bottom head usually had a green on top and a red on the bottom. Ocaisonally, though, you could find a block signal that had three lights (G-Y-R) on each head. That was the point of my question.
To further complicate things, the 1974 aspect chart for the CNJ shows signals with staggered heads, but none of the aspects show the lower head's yellow light actually lit on a staggered head signal.
But I guess I might be a little confused about how signal heads are normally used, I only had five years as a maintainer, four years as a manager, and four years as a signals superintendent, on two freight railroads and a light rail system.
