On this day in 1996, I was on a whirlwind tour of Chicagoland with the late Mike Abalos. We began our photography at Santa Fe’s Willow Springs yard and worked our way east through the industrial areas south of the Loop. My primary interest was photographing the myriad varieties of signaling active in the Chicago area, and Mike was just the man to get me to all the right places. This image was made near the end of daylight at State Line Tower. Throughout the day I was primarily using Kodachrome 25,working with my Nikon F3T, so this hastily composed photo was no exception. I was more interested in capturing the old Baltimore & Ohio Color Position Light signal than the CP Rail train about to pass it.

B&O’s unusual Color Position Light signals use a single-head to display all aspects. Key to interpreting the signal is the position of the white light that modifies the basic aspect. A ‘clear’ aspect is represented with two green lights in a vertical pattern (mimicking an upper quadrant semaphore) with a white light directly above them; when the white light is directly below the two greens, the aspect is ‘medium clear.’ With conventional color light signals a ‘medium clear’ may be represented with a three-head signal by red-over-green-over-red, or on a high two-head signal as red-over-green. The essential difference between ‘clear’ and ‘medium clear’ is the maximum speed allowed through an interlocking. A ‘clear’ aspect permits maximum track speed while a ‘medium clear’ limits speed typically to 30 mph. While fading light isn’t the best time to photograph moving trains, it is however a great time to photograph signals (because the signal lights appear brighter in comparison with ambient conditions). Thank you Mike!

Interested in railroad signals? See my book Railroad Signaling available from Voyageur Press/Quayside Publishing