Science & invention
William Potts
1883–1947 · police officer, inventor
Detroit police officer credited with inventing the modern three-color traffic light, first installed on Woodward Avenue in 1920.
- Born
Bad Axe, Michigan- Died
- Birth name
- William L. Potts
- Also known as
- William L. Potts
- Detroit years
- 1900s–1940s
- Field
- Science & invention
01 / The Detroit story
The Detroit story
Potts was born in 1883 in Bad Axe, in Michigan's Thumb, and was already listed as a police officer in the 1900 census. In Detroit he rose to superintendent of police signals as the city filled with automobiles and officers standing in intersections could no longer keep traffic moving. The red and green signals then in use gave drivers no warning that the right of way was about to change, so in 1917 Potts proposed an amber light that would shine between green and red. In 1920 he designed a four-way, three-color signal tower, installed on Woodward Avenue downtown, which let a single officer control an intersection from all directions. The three-color signal became the standard around the world, and the original 1920 signal is preserved at The Henry Ford in Dearborn.
Highlights
- Designed the first four-way, three-color traffic signal, Detroit, 1920
- Proposed the amber (yellow) warning light in 1917
- Superintendent of police signals for the city of Detroit
- The original 1920 signal is in the collection of The Henry Ford
02 / Their Detroit places
Their Detroit places 2
Where they lived, worked, performed and liked to hang out. Closed and demolished places stay here too, because they are part of the city's history.
Related place · 1920
Site of the first three-color traffic signal, Woodward Avenue
Demolished
Where Potts's four-way, three-color signal tower went up in 1920. Most accounts, including the Detroit Historical Society, place it at Woodward Avenue and Fort Street; Wikipedia names Woodward and Michigan Avenue. The tower itself is long gone.
Memorial
Henry Ford Museum of American Innovation
The first tri-color, four-way traffic signal from 1920 is preserved in the museum's collection.