Which inventor is credited with developing the manually operated, four-way signal incorporating the amber caution light?

Answer

William Potts

William Potts is credited with developing a four-way signal in 1928 that used the essential combination of red, amber, and green lights, making the caution indicator, or amber light, essential to modern signaling.

Which inventor is credited with developing the manually operated, four-way signal incorporating the amber caution light?
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