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The Origin of Traffic Lights

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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

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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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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May 23, 2017
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