Final answer:
Garrett Morgan invented the traffic light in 1923, adding a third signal, the yellow or amber light, to the existing red and green signals. His T-shaped pole design improved traffic flow and safety.
Step-by-step explanation:
Garrett Morgan invented the traffic light in 1923.
Before Morgan's invention, traffic lights used only red and green signals. He added a third signal, the yellow or amber light, to provide a warning before the change of signals.
Morgan's traffic light design consisted of a T-shaped pole with three lights on each side. This design allowed traffic to flow more smoothly and safely.