The stop sign got its octagon in 1923 via AASHO so drivers could recognize its priority from a distance, and it didn’t go red until the 1954 MUTCD when durable retroreflective red became feasible… As a traffic engineer I love that shape hierarchy (triangle for yield, diamond for warning) — does anyone know which city first fielded the octagonal STOP in practice?
When I’ve chased “who was first” on signs, the quickest proof has been city traffic orders — Detroit’s 1924 ordinances and police “traffic regulations” minutes show octagonal STOPs right after the 1923 AASHO spec, and FHWA flags Detroit as an early adopter: https://highways.dot.gov/public-roads/novemberdecember-2007/history-stop-sign; anyone have a confirmed pre-1924 field photo?
Quick tip: to prove “first in practice,” pull the 1923–1925 Board of Public Works annual reports and voucher registers — installation dates and invoices for octagon blanks pop up even when the ordinance lags; worth checking Detroit and a foil like Milwaukee, @chloe_ngu31. Want me to peek at Milwaukee’s 1924 report?