When was the Green Traffic Light Invented?

Traffic lights, commonly known as red and green lights, were invented before cars came into existence. In the early days, these lights were only used for trains and were lit using gas.


The history of traffic lights dates back to October 1868 when a signaling system was installed outside the British Parliament building in London. They were installed to signal passing trains. On a bracket-shaped pole, two gas lamps were mounted, one red and one green, to be used at night. The red light meant “stop” and the green light meant “caution.”

When were the red and green lights invented? traffic-light.jpgTraffic lights were invented before automobiles

In each lamp, gas was delivered through a valve system, and when a certain lamp needed to be lit, a police officer would turn the corresponding valve. This signaling system was extremely dangerous, and on January 2, 1869, just a few months after its operation, the lights exploded, injuring a police officer while he was adjusting them. Nevertheless, it continued to be used until the Americans invented electric traffic lights in 1912.

After the automotive industry developed significantly, a police officer named Lester Wire, working in Salt Lake City, Utah, USA, came up with the idea of applying railway signals to the road in 1912. At that time, railway signals were already automated, but since trains only ran on straight tracks and there were many level crossings with short clearance, they were not suitable and had to revert to manual adjustment.

In August 1914, the Traffic Signal Company was established in the USA and was responsible for installing traffic lights at intersections in Ohio. What was special at that time was that the traffic lights did not have a yellow light, so whenever they were about to change, the traffic police blew a whistle as a signal to the drivers.

By 1920, the system had all three colors – yellow, green, and red – and was patented by police officer William Potts, who lived in Detroit, in 1923. In the same year, Garrett Morgan received the patent for his traffic signal control invention, even though he was not directly responsible for the modernization of the traffic light system.

When were the red and green lights invented? gmorgan.jpgGarrett Morgan laid the groundwork for modern traffic signals

The motivation for Morgan’s invention came from the frequent accidents on American streets at that time. He realized the need for a standardized system for efficient operation of traffic signals. After research, Morgan designed a T-shaped signal post that included commands such as “stop,” “proceed,” and “stop in all directions.” Only when the light indicated “stop in all directions” could pedestrians cross the road.

Morgan’s systematic, strict, and advanced invention led to an unverified story. According to rumors, Morgan sold the patent for the traffic signal to the American electric company GE for $40,000, a significant amount of money at the time. GE then developed Morgan’s idea into the modern traffic light system. Morgan passed away in 1963 and was posthumously honored by the US government for his contributions to the traffic system.

After 1923, the traffic light system still required a human operator. Specifically in New York, more than 100 police officers had to work 16 hours a day, with a total salary of $250,000 per year. Because of these difficulties, engineers were ordered to develop an automatic control system. However, it took nearly 20 more years for the dream of traffic police to become a reality.

When were the red and green lights invented? 2014-08-05-Drevol-Blog-100-years-of-traffic-lights-600px.jpgNowadays, modern traffic light systems are much more advanced

Thảo Anh compiled (TTTĐ)