Permanent claim record · Detroit, Michigan

The world's first three-color, four-way traffic signal was installed October 20, 1920, at Woodward Avenue and Fort Street in Detroit by police officer William Potts.

Verified\u00b7 1920-10-20

Raw value (vault-stripped)

{"tags":["traffic-light","william-potts","inventions","firsts"],"text":"The world's first three-color, four-way traffic signal was installed October 20, 1920, at Woodward Avenue and Fort Street in Detroit by police officer William Potts.","as_of":"1920-10-20","category":"engineering"}

Predicate	trivia.fact
Subject	Detroit, Michigan (place)
As of	1920-10-20
Status	Verified
Source	Michigan Pop Culture, Game Shows & Trivia Content Mine — Perplexity Deep Research (March 2026) (trust 6.5/10)
Reference	—
Document hash	pending evidence-pack link
Provenance chain
Claim ID	03437685-6e0d-4c2c-b90d-79e102a5b4c7