Permanent claim record · Detroit, Michigan

William Potts borrowed the amber 'caution' light from railroad signaling; Detroit had 15 signalized intersections by 1921, and the three-color standard went national and global by the mid-1930s.

Verified
Raw value (vault-stripped) {"tags":["traffic-light","inventions","firsts"],"text":"William Potts borrowed the amber 'caution' light from railroad signaling; Detroit had 15 signalized intersections by 1921, and the three-color standard went national and global by the mid-1930s.","category":"engineering"}
Predicatetrivia.fact
SubjectDetroit, Michigan (place)
As of
StatusVerified
SourceMichigan Pop Culture, Game Shows & Trivia Content Mine — Perplexity Deep Research (March 2026) (trust 6.5/10)
Reference—
Document hashpending evidence-pack link
Provenance chain
Claim ID5d3c62d0-e63c-4630-b8f4-cd681257cc0e