William Potts

Who was William Potts?

William Potts, a Detroit police officer, is credited with inventing the modern, three-lens traffic light in Detroit in 1920.

William Potts was born in Michigan. The 1900 census lists Potts as 17 years old and a police officer. By 1910, he was married to Grace Potts, and they subsequently had 4 children. By 1920, Potts had become the 'superintendent, signal person police' for the city of Detroit. Charged with finding a way to control traffic and with the old system of police directing traffic increasing outmoded, Potts invented a 'yellow' or 'amber' light which removed the need for police to switch the signal.

The first four-way traffic signal tower in the world was located at the Woodward and Michigan Avenue intersection in October 1920. The tower was manually operated and had 12 lamps, three in each direction. In December 1920, signals were added along Woodward Avenue at Grand River, State, Fort and Congress, but all were controlled from the manual tower at Woodward and Michigan.

Then in 1921, Potts, who was a Superintendent of Signals for the Police Department, installed his first automatic signal light system in 15 towers. During the next 25 years the location and operation of traffic lights throughout the world changed considerably, but the original principle developed by Potts remained. The last traffic tower in Detroit was removed from East Jefferson and Grand Boulevard in 1930. The traffic light system has been modernized with corner posts, hanging center lights and mast arm extensions.