Old Oregon drawbridges used to use these single horizontal signals - the first one was green in the center with yellow on both ends (which flashed when the bridge was up) and the second one had red on the left, green in the middle, and yellow on the right. All 3 bridges connecting Astoria and Warrenton, OR on US 101 used to have them, but they were slowly phased out with the last one being removed around 2016.


(Best pictures I could find on Street View, I don't have any of my own and can't find others that show the color of the signals.)