The Stops And Starts Of Designing The Traffic Light

You might not realize it when you've been trapped behind the same red light for five minutes, but traffic lights, when they're timed and tuned correctly, are actually pretty good at making traffic move. Really.

Traffic lights, believe it or not, organize fast-moving cars into groups based on the time of day and road usage, smoothly sending them through intersections that might otherwise net (a lot more) headaches and insurance claims.

But it took a flood of cars—the half million in 1910 that skyrocketed to nine million 10 years later—to make us realize that traffic, especially where roads meet, can be a dangerous problem. It wasn't just cars competing for the right of way—horses and bicycles were also vying for a place on the road. At the time, crossroads were mediated by hand waving, an attending officer, or a game of chicken.

City-dwellers were the first to seek a solution. An early traffic signal model made in Chicago in 1910 had the words, "Stop" and "Proceed" visible to drivers. The instructions didn't do much for evening travelers, though, as the sign had no lights.

Another model popped up in Salt Lake City two years later, designed by someone who knew the importance of an effective signal: a police officer. Lester Wire invented the first traffic light that actually lit up. His device, made in 1912, was basically a box with two circles carved in the front. A red light and a green light placed in the openings told vehicles whether to stop or go.

But a stoplight invention wasn't patented until the early 1920s, when Garrett Morgan, an inventor in Cleveland, Ohio, witnessed a terrible collision between a car and a horse drawn carriage that left a girl seriously injured.

Morgan realized that one of the problems with current signals was that the transition from go to stop and back again was too abrupt. The signs, he thought, should instead have an in-between indicator that warned people to slow down before the traffic flow changed directions.

His design, which was operated manually and shaped like a cross, incorporated "a visible indicator which is useful in stopping traffic in all directions before the signal to proceed in any one direction is given," according to his 1923 patent. An attendant operated a crank to fold the arms of the cross upwards. When the top and side-pieces were all lined up vertically, the device displayed the illuminated word "Stop." An alarm bell option attached on top like a hat to further punctuate the four-way stop. When the intersection was cleared, the attendant swiveled the signal, and the word "Go" faced the oncoming traffic.

Now for the sad part of the story. Morgan sold the patent to General Electric for $40,000. (Okay, maybe it doesn't sound that sad, since that's more than half a million dollars in today's money.) But the reason he sold the patent, rather than developing the stoplight himself and becoming richer than Jesus Christ's rich uncle is because he was an African American. And this was not his first lifesaving invention! Some years earlier, he and a group of volunteers used a gas mask he designed to save workers trapped in a tunnel being dug under Lake Erie that had collapsed. When news got out of his heroic actions and the gadget that made the rescue possible, orders flooded in. But when buyers discovered that Morgan was African American, nearly all the orders were canceled. Fearing he would experience similar problems with his traffic light, he sold his idea. Horrible.

Automatic lights soon replaced the manual set up, but Morgan's three-action system was clearly the precursor to the traffic signals we rely on today. He invented other indispensable stuff throughout his life, too, creating the first chemical hair straightener and a self-extinguishing cigarette filter. Just before his death in 1963, the U.S. government honored Morgan with an award for his groundbreaking work in road safety.


Rachel Swaby is a freelance writer living in San Francisco. You can keep up with her on Twitter.

Image: CC licensed, Flickr/vizzzual.com