Garrett Morgan Saw a Crash at an Intersection and Invented the Yellow Light

US1475024 was granted to Garrett A. Morgan on November 20, 1923. The title is "Traffic Signal." Morgan is better known for the safety hood he wore into a gas-filled tunnel under Lake Erie in 1916, but the traffic signal is the invention most people encounter several times a day without knowing his name.

Morgan was one of the first Black car owners in Cleveland. Automobiles, horse-drawn wagons, bicycles, streetcars, and pedestrians were all sharing intersections that had no established rules, and the results were routinely violent. The version Morgan gave was that he witnessed a severe collision between a car and a carriage at an intersection and decided the signalling was the problem.

Two states are not enough

The traffic signals of the era were essentially binary. A semaphore or a manually operated sign displayed STOP or GO, and an operator flipped between them.

The flaw is one every driver understands intuitively. If the signal switches instantly from GO to STOP, the vehicles already in or approaching the intersection have no defined moment to clear it. Cross traffic starts moving while the previous traffic is still in the box. The transition itself is the dangerous part.

Morgan's patent adds a third position. Before the signal changes direction, the arm moves to a state that halts traffic in all directions simultaneously, clearing the intersection before the opposing flow is released.

That is the conceptual ancestor of the amber light and of the all-red interval still built into modern signal timing. Morgan's version was mechanical — a hand-cranked, T-shaped post with a rotating arm, not colored lamps — but the logic is the one traffic engineering still uses.

Sold for forty thousand

Morgan patented the design in the United States, Canada, and Britain, and sold the American rights to General Electric for a figure usually reported as forty thousand dollars — a substantial sum in 1923, and considerably better than most inventors in this archive managed.

Electric three-color signals developed along a parallel track; several inventors and municipal engineers contributed to the modern lamp-based traffic light, and Morgan was not the sole originator of the traffic signal as a category. What his patent captures is the specific insight that a signal needs a transition state, not just two commands.

The context

Morgan built a substantial life as an inventor and businessman in Cleveland — a sewing machine repair shop, a tailoring company, a hair-care products company, and a newspaper — in an era when doing any of that as a Black man in the United States required navigating constant, explicit obstruction. He had earlier hired a white actor to pose as the inventor at demonstrations of his safety hood, because buyers cancelled orders when they learned who had made it.

The yellow light is his. Most drivers have never heard of him.

See the original

The full text and figures of US1475024 are on patents.us.