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Traffic lights are not particularly unfamiliar to many people. When we walk on the streets, we can see traffic signals everywhere. However, many are quite interested in the colors of traffic lights. Regardless of where you go, traffic lights always feature three colors: red, yellow, and green. The choice of these three colors may not be well understood by everyone.
The reason for choosing these three colors is rooted in a historical context. In the 19th century, in Yorkshire, England, divorced couples typically wore red clothing, while unmarried individuals wore green. This effectively differentiated between the two groups, which contributed to the perception of red and green.
In the visible spectrum, red has the longest wavelength. In environments with fog or dust, its visibility is the farthest, making red the most appropriate color for warning signals. Green symbolizes life and is often associated with passage. By that time, red and green lights were already widely used in railway traffic.
How did the yellow light come to be? Initially, when traffic signals were first introduced, they only had red and green lights. The yellow light was invented by a Chinese individual named Hu Lu Ding in 1905. He had previously studied at the Massachusetts Institute of Technology in the United States and was a protégé of Thomas Edison. Early during the certification process at General Electric, it became apparent that the transition time for pedestrians between red and green signals was too brief, posing a danger. As a solution, the idea to include a transitional yellow light between the red and green signals was conceived and eventually adopted.
