As RVers, we rely on them. They are one of the best ways to prevent traffic accidents and to keep motorists moving smoothly on the roadways today. But did you ever wonder how it happened? How was the traffic light invented in the first place? I wondered about that, too. Here’s what I discovered.
It may be hard to believe, but traffic jams and accidents were prevalent even before the automobile was invented. It was in London in the 1860s. Horses and carriages, along with throngs of pedestrians, jammed the streets, and a British railway manager thought he knew how to solve London’s bustling and often harrowing traffic problem.
That railway manager was John Peake Knight. Because Knight was familiar with how trains were controlled, he wondered if street traffic might be able to adapt and use a similar system.
Knight invented a semaphore system that could be operated by a police officer. (A semaphore is basically a pole with moving “arms.”) In Knight’s traffic control system, the police officer would move the signal arm to “stop” and/or “go” during the daylight hours. At night, officers used gas lamps to illuminate the signals. The signal indicated “stop” by implementing a red light and signaled “go” with a green light.
In 1868, the first traffic signal was installed. Just one month later, the traffic signal operator was seriously injured when the gas lamp exploded in his face. Knight’s invention was deemed a public health hazard and the traffic signal idea was abandoned.
Early American inventors
In 1910, an American inventor, Ernest Sirrine, developed a traffic signal in Chicago. Sirrine’s signal featured display arms much like John Knight’s original idea.
Then in 1912, a police officer in Utah, Lester Farnsworth Wire, came up with a different iteration of the traffic signal. Wire’s signal looked a lot like a four-sided birdhouse. Wire positioned the signal on a tall pole in the middle of the intersection. Because electricity had been invented by this time, Wire’s invention was powered by the same wires that operated the trolley system. Wire’s traffic light still relied on a policeman to activate the signal, however.
James Hoge is usually credited with inventing the “first electric traffic signal.” Hoge received a patent for his traffic light in 1918. His signal alerted drivers with the words “stop” and “move.”
Other inventors followed. William Ghiglieri first patented a red and green signal light in 1917. In 1920, a police officer from Detroit, William Potts, developed several automatic traffic light systems. He was the first inventor to add a yellow “caution” light to his signal.
Garrett Morgan is the inventor credited with designing what most nearly resembles the traffic lights we see and use today. Morgan was the first African American to own a car in the city of Cleveland. His traffic signal design featured a three-light canister fastened on a pole. It was patented in 1923.
At the time, motorists had no warning when the light would change from green to red. This was the cause of many accidents. Morgan figured it would be safer for all traffic to be stopped in all directions before the light color changed. This would allow drivers time to come to a stop or proceed safely through the intersection. Morgan’s signal design was beautifully simplistic and could be mass-produced quite inexpensively. He eventually sold the rights to his invention to General Electric for $40,000.
Why red, green, and yellow?
You might wonder about the colors used and why the colors are arranged with red on top, yellow in the middle, and green on the bottom.
The earliest traffic signals were designed for trains. Red, the color of blood, has been known to represent danger in many cultures all over the world for centuries. Red also has the longest wavelength of any color in the visible light spectrum. It can be seen from the farthest distance.
Directly across from red on a color wheel, green is a natural option for the opposite of red. “Green means go” also hearkens back to the railroad days. At first, trains used red for “stop” and white for “go.” But because white was difficult to see in the bright daylight, trains switched to the color green.
Yellow or amber has the second longest wavelength in the light spectrum, so it can be seen from almost as great a distance as red. It seems to be a logical choice for the “caution” light.
Traffic light color positions
Ever wonder why the red signal is on top of traffic lights? Most folks say it’s because stopping is so important red takes the top position. Yellow takes the middle position because of the lighting sequence (green, yellow, red). Green is at the bottom of the traffic light because of the light sequence and also to help people who have trouble distinguishing between red and green (color blindness).
Some traffic signals are positioned horizontally—presumably for safety, according to some folks in the DOT—though not everyone agrees. Horizontally mounted lights can be held in position on the wire with two or more attachment points, which may hold the light system more securely during extremely high winds.
Well, there you have it! The next time your RV rolls to a stop at a traffic signal light, you can impress your travel buddy with what you’ve learned. Travel safely out there!