OK, here's a real trivia question that has stumped me. The 1935 standard plan
for wayside signals which was adopted by the Van Sweringen roads specified
that, on a three-signal-head color light interlocking signal, the color lights
of each signal head would be ordered, top to bottom, as follows:
Top: Red-Yellow-Green ("traffic light order")
Middle: Yellow-Green-Red
Bottom: Red-Yellow-Green
Does anyone know why this was? What was the theory?
Reviewing the books I have at hand, it's evident that this standard was
generally complied with on the Erie and NKP at least, but I also see some evidence
that by the 1970's the specified order had fallen into some disarray.
WDB
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