Let's Take A Closer Look

Explaining complicated subject matter simply since 1986

Three is the smallest number that can play the outdoor children’s game called Red Light, Green Light, but it’s more fun with large groups. One person is chosen as the Stop Light and all the rest of the players line up behind the Starting Line, which has been set 10 or 20 yards from where the Stop Light is standing. 

The game begins when the Stop Light, back turned to the players, yells “Green Light!” This is the signal that allows players to closer to the Stop Light The object of the game is for a player to get to the Stop Light without being caught. At any time, the Stop Light (still with back to the players) can yell “Red Light!” then turn around quickly to try and catch anyone still moving. Anyone caught moving gets sent back to the Starting Line. 

The Stop Light turns away from the players again and yells “Green Light,” beginning another cycle of getting caught/not getting caught while advancing on a Red Light. The player who is first to tag the Stop Light is the winner and gets to become the Stop Light until tagged, and so on.

What do stoplights* have in common with the national flag of Ghana?

They both use a red-yellow-green system where each color has a meaning behind it. In 1957, Ghana was the first black sub-Saharan African country to gain its independence from British colonial rule.

  • Red symbolizes the struggle for independence.
  • Yellow stands for the country’s wealth.
  • Green represents its forests and farms.

Other newly-independent African nations (twenty-six from 1951-1960) chose red, yellow, and green for their flags, too, indicating a sense of solidarity between all the African nations. Take a guess at how many African countries have red, yellow, and green flags.**

Everyone knows what the three colors of the flag of the United States of America stand for, right?

George Washington said the red symbolizes England, our mother country, and the white represents liberty. Flagmaker Betsy Ross said each star indicates a colony, the red stripes stand for the blood of sacrifice, and white stripes symbolize love and peace. Together, thirteen stripes indicate the thirteen original colonies. The original number of stars was thirteen, with another added each time a colony achieved statehood, all the way up to today’s 50. Stars were chosen because they’re symbols of the heavens. 

Down to the sea in ships

In 1838, Martin Van Buren was president of the United States. He signed into law an act that required that powered ships display one or more signal lights when operating at night. It wasn’t until 60 years later that the agreed-upon rules and regulations were adopted internationally. They established specific requirements and laws for all marine and maritime activities, the primary intent being to avoid death and destruction.

Four lights were mandated

At the bow and stern were white lights. On one side was a red light and on the other, a green light. In seafaring parlance, left is called port and right is called starboard. I could never remember which was where until someone told me port has the same number of letters as left and port wine is red. Left=port=red. A red light is mounted on the left side (when facing forward) and a green light on the right. The standardized arrangement of the lights allowed sailors to swiftly determine another ship’s postion, heading, and relative size.

Trains

After the Civil War, thousands of miles of track carried hundreds of trains at once and the number of train crashes and passenger deaths increased every year until a few people decided to do something about it. Some of those deaths were prevented by getting all railroad lines on the same timetable. This led to the creation of time zones in 1883. The other was to replace semaphores with a color-coding system all would recognize. Red lights trackside and on the last car of every train said Danger! Stop! Green indicated to engineers that the track ahead was clear. The bright light at the front (headlight) oscillated so it wouldn’t be confused with any other light source.

Airplanes are the ships of the sky

Just like ships, every airplane is required by law to follow the red/left, green/right, and white fore and aft format. The additional stipulation is that lights must illuminate the extremities of the aircraft’s structure, including the bottom of the fuselage and the top of the thing airplane people call the vertical stabilizer. The rest of us call it a tail.

Jessica Deere is a Museum Coordinator

She heads up The Grimes Flying Lab Museum .Deere told me that Warren Grimes was the inventor of aviation lighting and is known as the father of the aircraft lighting industry. Grimes’ first lighting design and installation was for Henry Ford’s Ford Tri-Motor civilian and passenger airplane. The Tri-Motor was nicknamed the Tin Goose because it was one of the earliest planes made of metal and not the traditional fabric-covered wood. It makes good sense that they copied the red/port, green/starboard standard used by ships since 1838. 

The earliest traffic signals were made by policemen standing in the middle of the intersection

They first used hand signals and gestures to indicate who should stop and who can go. Then they operated stop and go signs. Too many injuries to the policemen meant they would soon be replaced by traffic signals.

In the early days of automobiles, states, cities, and towns had their own ideas about how traffic signals would indicate stop and go

These many different interpretations of how the signals for stop and go should be indicated led to many collisions, injuries, and deaths. It was finally agreed that automobiles should follow the red/green system already used by other means of conveyance. The difference would be that the signal lights would not be mounted on the cars, but at intersections where there was a need to control traffic, especially in cities. The traffic lights would control intersections by giving the right of way to some traffic while forcing cross-traffic to wait their turn, thus making the intersections safer for motorists

In 1912, Lester Wire invented the electric red and green traffic light

Eight years later, the design was modified by the addition of an amber light between the two. It was believed that replacing the abrupt transitions between red and green with a third color would indicate the change from go to stop was only seconds away. Given that it has already been determined that red and green are two of the three colors, the ideal hree-color combination is red, green, and blue (just like your RGB televisions). But blue was too much like green with the existing lighting technology. So for a color also midway between red and green, the next best thing to blue was its opposite, yellow. And so it was finally settled that red means stop, green means go, and yellow means caution, or as Mork said, observing life on earth, “Yellow means go really fast.”

Why the top-to-bottom red-yellow-green sequence?

The standard that was adopted was to put red on the top and green on the bottom. This came about when someone who took a closer look at accidents occurring at intersections realized that colorblind people relied on the position of the light to tell them to stop or go. Standardization of colors and sequence drastically reduced collisions involving not only colorblind drivers, but others, too. Red-yellow-green is so ingrained in our culture that even small children know it.

Are amber and yellow the same color?

They’re close, but amber sits between yellow and orange, a position that puts it squarely in the middle between red and green. Take a closer look at your traffic lights. Are they amber or yellow?

If you’d like to know more about U.S. rules for drivers, the Federal Highway Administration just released its 11th Edition a few months ago. It includes chapters on signs, signals, markings, and traffic control. It’s available here as a .pdf.  

Bonus

 *  *  *

*Industry purists call them traffic signals, but most Americans call them traffic lights or stoplights.

** 20 African countries use red, yellow, and green on their flags.

 

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