Questions and Answers

Why Are Stoplights Red, Green and Yellow?

Photo by [Stuart Miles]

You know here in America and probably many other countries stoplights contain a red light, green light, yellow light and sometimes a green arrow. Stoplights haven’t always been that way and it’s pretty interesting to find out why stoplights are red, green and yellow.

There’s actually some pretty good explanations for this and most of the history that formed the modern day stoplights came from ideas used in the railroad systems.

Red, Green and Yellow stoplights Grandfathered in From Railroads

Red, green and yellow traffic lights were used in the railroads as a means for controlling trains on the tracks.

Red was chosen by the railroads as a signal for “Stop” mainly because the color red had been associated with danger for thousands of years. So it really makes sense, especially if danger means getting hurt and getting hurt often times leads to bleeding, and what color is blood? That’s right, it’s red too.

Back in the 1830s and 1840s railroads were just beginning to transport goods and people across the country and the color red was a pretty easy solution for getting them to stop. But the other two colors haven’t always been as they are today. In fact, the green light used in railroads during the early eras as a signal for “caution”. Where as green means “go” today, but it was actually a clear, or white light that was the original signal for “go”.

But this color combination posed some serious safety risks. For instance, an ordinary street lamp would be easily mistaken for a white signal light and the train engineer would think, “Awesome, let’s keep truckin’ forward” that could lead to potential danger if it wasn’t safe to go. There was even a time that the red lens cover for the “stop” light had fallen out and all that remained was the white light. Well the engineer seeing the white light thought it was safe to go forward and not slowing his train led to a terrible crash.

Modernizing the Stoplights

As you can see these early attempts at a signal system sort of failed, so they had to come up with something else. Inevitably they decided to use red to stop, green for go and yellow for caution. This way if one of the lenses fell out again the engineer would realize something wasn’t right because there should be any white signal lights. This would allow the engineer ample time to stop his train and check on the situation.

Seeing how the train system had already done all the leg work in perfecting a signaling system it was quite easy for modern road traffic engineers to adopt the same system. So they decided to borrow their technology and implement it into traffic signals for automobiles.

In 1914, the first traffic signals were installed in Cleveland, Ohio and only contained a red and green light. I suppose they though that was all that was really necessary for automobile traffic. But within a few years time, the yellow light was also added to the signals which made traffic accidents much less likely. The yellow, or “caution” light would allow an automobile plenty of warning that a red light was fixing to occur.

The system worked perfectly so it’s been that way ever since. But let’s please remember folks, that yellow is a signal for “caution”, not “go faster!”

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6 thoughts on “Why Are Stoplights Red, Green and Yellow?
  1. Great post. Yea indeed folks need to make the difference between the yellow and red light cause now a days folks see yellow light as a sign that says “go fast quick”.

    1. Yah it’s really quite crazy Tarik. It’s not normally the first one to fly through the yellow light that disturbs me, but the 5 or 6 others that pass through the light after it’s already turned red…lol

  2. Interesting post that enlights us why the stoplights have these colors instead of others! Thank you! The only thing I knew is that the red lights settled as one of the stoplights as it catches your attention easily and sometimes means danger!

    1. Glad you enjoyed the information. The red light was most definitely picked for specific reasons one of which you already mentioned. But I think it’s kind of funny how the green and yellow were basically pulled from a hat. If you think about it, there’s tons of cliche sayings that now include using a green light or the color green symbolically as “everythings safe”

  3. I have serious concerns about people zipping through the yellow light, my mother was hit by a driver running a red light, which the driver claimed was yellow when she continued driving. All the same it is more dangerous than running a red light. I also learned something new from this post, I did not know the first traffic light was in Cleveland, Ohio learn something new everyday.

    1. I have to agree C.A that running yellow is probably more dangerous than a red. There are probably more accidents caused by people trying to hurry through a light that way. If the lights were used as intended then it wouldn’t be nearly as bad. But the world is in such a big hurry these days in everything that’s done. I think everyone needs to slow down and smell the roses, ya know?

      I’m sorry to hear of your mother’s accident, hopefully the instigator was insured. Thanks for reading and I’m glad you enjoyed the post.

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