“Only 39 states issued them [driver’s licenses] by 1935 and few required a test, despite widespread concern about incompetent drivers. Early motorists were taught to drive by automobile salesmen, family and friends, or organizations like the YMCA. By the 1930s, many high schools offered driver education.”
By the 1920s, congestion, accidents, and parking problems clogged city streets. Cities imposed speed limits, installed traffic signals, and tried one-way streets, parking restrictions, and parking meters to keep vehicles moving.
More traffic also meant more traffic laws. William P. Eno, a crusader for better traffic management, composed “Rules of the Road” and other traffic guides, which became the basis for many cities’ traffic laws. Traffic management, road maintenance, expanded police departments, and new construction ate up large segments of municipal budgets, and cities looked for new sources of revenue to cope with the presence of motor vehicles.”
“In the 1920s, traffic towers enabled police officers to see above trucks, trolleys, and heavy traffic as they operated signals.”
“Semaphore signals were common in cities in the 1920s. During the late 1920s, three position signals—the red, amber and green we know today—began to be used, and eventually became the standard.”
America on the Move