The History of Traffic Lights: From London Gas Lamps to Fifth Avenue Towers

The first traffic signal was installed outside the Houses of Parliament in London in 1868 — a gas-lit semaphore operated by a police officer — and it exploded within weeks. The first electric traffic light in the U.S. appeared in Cleveland in 1914, the familiar three-color red-yellow-green signal was developed in Detroit around 1920, and New York’s Fifth Avenue famously used elevated traffic towers in the 1920s. Today’s traffic lights are computer-controlled, and New York has one of the densest signal networks in the world.

Timeline

London, 1868

Railway engineer John Peake Knight adapted railway semaphore arms for road traffic outside Parliament, with red and green gas lamps for night use. A gas leak caused an explosion that injured its police operator, and the idea was abandoned for decades.

Cleveland and Detroit

As car traffic grew, American cities experimented with electric signals. Cleveland installed an electric signal with red and green lights in 1914. In Detroit, police officer William Potts developed a three-color signal around 1920, adding an amber “caution” light.

New York’s traffic towers

In the 1920s, Fifth Avenue had elevated towers in the middle of the avenue, where police officers controlled signals for traffic in both directions. The ornate bronze towers became landmarks before they were replaced by automated signals.

Garrett Morgan

Inventor Garrett Morgan, a Black entrepreneur from Cleveland, patented a traffic signal in 1923 with an intermediate “stop in all directions” position. He sold the patent to General Electric.

Traffic signals today

Modern signals are coordinated by computers, with timing adjusted for rush hours. In Manhattan, signals on avenues are often timed so a car moving at the speed limit hits successive green lights — the “green wave”. Read NYC traffic by hour and why not to drive in Manhattan.