An archival film from 1937 explains how automatic traffic signals worked in different cities across the country
Via my Atlantic colleague Kasia Cieplak-Mayr von Baldegg, check out this educational film produced by Chevrolet in 1937, titled Seeing Green. It's easy to forget that at one point in our history, there was no national standard that red meant stop, and green meant go — many cities operated their own unique versions of automated traffic signals, some with four colors, and others with only two. The film also explains some of the basic mechanics of how lights were coordinated across a city at the time.
To watch this film in its entirety, visit the Prelinger Archive.