In the Beginning
The Origin of Traffic Lights
by In the Beginning - February 8, 2010 - 6:25 PM

Editor’s Note: Reader Andrea recently asked if we could cover the history of traffic lights. Here’s what we had in the archives. –Jason

redlightgreenlightII.jpg

We’re still stumped on that whole chicken vs. egg question, but there’s one thing we do know for sure—traffic congestion predates the automobile. Long before the invention of the internal combustion engine, horses and people were already having so much trouble yielding to each other at intersections that, in 1868, a British railroad engineer designed the first traffic signal to help them out. Oddly, the contraption only featured two settings: “stop” and “caution,” indicated by a bar held horizontally or lowered to a 45-degree angle. At night, red and green lights were used to make the bar visible, meaning that, in this case, “green” meant “slow down.” A proclamation issued by London’s police commissioner in 1868 explained the system as well as the then-novel concept of pedestrian right-of-way, and for the first time, cities had a way to keep people from constantly running into each other.

Control Tweaks
The concept of a box with bars sticking out each side like arms was modeled on the naval semaphore system, a way of communicating between ships where a sailor would hold certain flags at certain angles to create messages. As overly complicated on the street as it was on the sea, it soon fell out of favor, replaced by an electrical upgrade. The first light-based traffic signals were probably those installed in Salt Lake City by police officer Lester Wire in 1912. Featuring a slanted roof to shed rain and snow, Wire’s signal boxes contained dye-colored lights that shone through coverless circular openings and were powered by the same wires that ran electric trolleys. Like the earlier signals, Wire’s lights only had two settings, in this case “stop” and “go,” and were manually operated on-site by a police officer. A similar system was installed (and patented) in Cleveland in 1914, but with a significant safety improvement. Unlike their Western counterparts, the Cleveland lights were all connected back to the same control station and wired so that it was impossible to accidentally tell both directions to “go” at once (an important development, no doubt).

Amazingly, the first three-setting lights didn’t come along until the 1920s. Based on railroad signs being used since 1899, the three-light signal first appeared in Detroit and New York City between 1920 and 1922. These cities were also on the forefront of an effort to streamline traffic signal controls (and thus improve the flow of traffic in general) by wiring several different intersections back into a single control tower.

This article was written by Maggie Koerth-Baker and excerpted from the mental_floss book In the Beginning: The Origins of Everything. You can pick up a copy in our store.

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Comments (13)

  1. Here in the Philippines there’s no such thing as traffic signals… :)

    posted by Jay-R on 9-22-2008 at 12:50 am

  2. Don’t forget my home town – Carmel, Indiana home to the first electronic automated traffic signal; installed in 1923.

    posted by Kristin on 9-22-2008 at 7:21 am

  3. what city is pictured above? it looks like maybe New York or Chicago

    posted by kat on 9-22-2008 at 10:53 am

  4. Kristin – really? Do you know what intersection?

    I’m from Noblesville, by the way.

    posted by Anne on 9-22-2008 at 12:54 pm

  5. Carmel, Indiana – Courtesy of wikipedia…

    In 1924, one of the first automatic traffic signals in the United States was installed at the intersection of Main Street and Range Line Road. The signal that was installed was the invention of Leslie Haines and is currently in the old train station on the Monon.

    posted by Todd on 2-8-2010 at 7:28 pm

  6. That’s New York, on or about 14th Street and 9th Avenue, which is also where you’ll find our unofficial Manhattan office (also known as The Diner).

    posted by Jason English on 2-8-2010 at 7:46 pm

  7. I heard there are new LED traffic lights coming out in some parts of the country, the only problem with them is that is snowy areas the lights do not generate enough heat to melt away the snow that gets built up

    posted by jodie on 2-8-2010 at 8:06 pm

  8. Heh. I lived in the Philippines for 15 years. Driving in the Philippines is like a real life “Need for Speed”. Crazy man. I get honked at if I’m at a stop sign and there is no opposing traffic. Nutso, man. That ain’t even half of it…

    posted by Kevin on 2-8-2010 at 11:47 pm

  9. How could you cover the history of traffic lights without giving a shout-out to the inventor, William Potts?

    William L. Potts, a police officer from Detroit, Michigan, decided to invent the traffic light due to problem caused by the increasing number of cars on the streets.

    Jason, here’s a wag of finger.

    posted by Lori on 2-9-2010 at 6:48 am

  10. as evolution is pretty much proven as fact, it is clear that the proto-chicken laid an egg and a chicken then hatched. The egg came first.

    posted by ee the c on 2-9-2010 at 8:24 am

  11. What a coincidence, Jason – my unofficial office is known as The Diner too!

    posted by B on 2-9-2010 at 12:08 pm

  12. Ah yes..the Philippines. I still live there…10 years now. I’ve seen traffic lights. Outside Manila they rarely have power supplied…and even when illuminated, are routinely ignored. Truly…a free country!!!

    posted by top-n-bottom on 2-9-2010 at 3:18 pm

  13. Todd…. sorry to bust your bubble, BUT wiki is the worst source of information… Find a more reputable source of information….. to prove my point read the news story about the reporter who used Wiki to quote a foriegn diplomat/politician and the quote was never spoken by this man

    posted by jeremiah on 2-9-2010 at 5:01 pm

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