Why are traffic lights Red, Yellow and Green?

Color is a silent language that affects our behavioral response in our daily lives. It can also be a learned response that can cause us to respond in a certain way based on our cultural background. For example, what would you think of a man in a pink outfit, underwear or shoes? A learned response is also responsible for the color preferences that we have through our experience of past events in our daily social life. A behavioral response on the other hand happens naturally without us being aware of it. For example, the color red can heighten our perception of danger just by seeing it - the color of blood. It can also cause sensations of excitement and warmth - which is a color used to express love such as valentines day and the red heart to represent love. Nevertheless, with regards to the traffic light, we all know that from our everyday experience - a learned response - that a red light means “STOP“ (and I really have to assume this since some people always fly across this red light at traffic intersection to the detriment of others), a yellow ( or amber) light means “ SLOW DOWN” - approach with caution and prepare to stop while green light means “GO” - if it is safe to do so. This weeks article will answer the question above and don’t go feeling that you know or have the answer (idea) to this question based on what you just read!

How It All Started

The colors used by automobile traffic light system was originally adopted from the color code system used by railroad engineers as a traffic signal devised to control the trains on the railroad. This color system was used on railroads to prevent fatal train collisions and thus this traffic signal device was implemented to reduce train collisions by providing trains with advance warning of danger.

The first choice of color that was selected to be used by the rail road engineers to represent a stop signal was the color red. This color - the color of blood - was selected because it symbolizes danger or warning thus, it was logically the most likely choice to get the attention of anyone. It sends the message that if ignored, there could be very serious consequences such as serious injuries or death. Therefore this color was selected to symbolize the signal stop.

For the other two colors, railway traffic light being a new system at the time, railroad engineers experimented with the colors green which was the color for "caution" and white (clear) which was the color for "go". However, in the 1830s, these traffic signals lights were colored by using red, green and clear filters. Due to the use of these filters some very serious train collisions would occur. This problem would stem from the fact that the street lights, distant stars, glare of the sunlight and other lights could easily be mistaken for the “go” light. In addition to this, sometimes the red filter of a "stop" traffic signal would fall out leaving the bulb emitting white light which in a sense would be signaling the message “go”. To correct this problem engineers made modifications where red light would be the signal “stop”, yellow light “caution” and green “go”. This move solved the problem of filters falling out. Whenever a white light signal is seen this indicates that something is wrong with its signal lamp and it needs to be corrected right away.

Traffic officials during the horse and buggy days, were facing heavy traffic in big cities which put great pressure on police officers who had to be stationed full time directing traffic at busy intersections. In addition to this, the situation was about to become worse with the coming of automobiles. Due to the fact that the railroad traffic color system worked so well with the railroad system, it was readily adopted for automobile traffic light system. This adoption came through a police officer name William Potts of Detroit, of Michigan. He came up with an idea to rectify this problem by using the railroad traffic signal system. This he achieved by using the same scheme of colors of the railroad traffic and using wires and electrical controls to make the world’s first 4-way three color traffic light. This was installed in Detroit (on the corner of Woodward and Michigan Avenues) in 1920.

During this time, African American Garrett Augustus Morgan (1877-1963), seeing the need of a control traffic flow invented the electric automatic traffic light. This was installed in Cleveland, Ohio in 1914 and had only two lights: red and green. However, the yellow light was added after the need for a "caution" light became crucial for the traffic signal to serve its purpose effectively. This set the foundation on which modern four-way traffic lights are built.

Garrett Augustus Morgan also invented the gas mask, in the early 1900s which was used by firemen and also by soldiers in World War I.

Did you know?

Color blindness
In order to help support people with red-green color blindness, red light contains some amount of orange in its hue, and the green light contains some amount of blue. This helps to identify the red and green light.

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