This Is Why Traffic Lights Are Red, Yellow, and Green

The First Stoplights

The first traffic lights in the United States were installed due to an increase in travelers on the road. In order to avoid accidents, many cities and towns installed traffic lights to better control the flow of cars. Officers manned the towers and used whistles as well as lights in red, green, and yellow to give drivers instructions about when to stop and go.

In 1920, William Potts created the first tri-color, four-direction traffic signal. It kept drivers safe even at intersections. The very first four-direction traffic light was installed at Woodward Avenue and Fort Street in Detroit, Michigan. But since America is a big country, there were still different systems for traffic lights in different regions, which could end up causing problems for drivers. So the Federal Highway Administration created “The Manual on Uniform Traffic Control Devices” in 1935 that set uniform standards for all road signs, pavement markings, and traffic signals requiring them to all use red, yellow, and green light indicators.


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