Traffic signals: A brief history | Washington State Magazine
: In 1908, Henry Ford introduced the Ford Model T , which became so popular that by 1914, he adopted assembly line methods to meet soaring demand. 100 Years Evolution of traffic - 1910s till the 2010s
: In the 1930s, the first barrier crash tests were conducted by General Motors . Traffic signals: A brief history | Washington State
: The first electric traffic signal in the U.S. appeared in Cleveland (1914) , controlling a mix of cars, streetcars, and horse-drawn carriages. appeared in Cleveland (1914) , controlling a mix
Post-depression and war eras saw a focus on expanding road networks and basic automation.
: The first drunk driving law was enacted in New York in 1910 . 1930s – 1950s: Infrastructure & Computerization
: In 1920, Detroit police officer William Potts invented the three-color electric traffic light , adding an amber (yellow) light adapted from railroad signals.