Why Japan Has Blue Traffic Lights Instead Of Green

A blue-green traffic light attached to a pole in Japan

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The land of the rising sun is a fascinating mix of history, founded on strong tradition, and the latest cutting-edge tech. For automotive enthusiasts, car spotting in Japan is on another level, offering a variety of makes and models, each sporting its own rad cultural flair. And then there’s the blue-green color on some traffic lights — implemented as a compromise between common Japanese vernacular and U.N. treaty standards.

A United Nations treaty, the Convention of Road Signs and Signals, was signed by 35 countries in 1968, and has since been incorporated into 75 total (although neither the U.S. or Japan have signed). This treaty includes Article 23 — Signals for vehicular traffic — which essentially states that green means go, and red means stop.

Traditionally, the Japanese language used the same word for blue and green, “ao.” So the bureaucrats of Japan had a predicament. The word for green is now “midori,” but with the Japanese people associating the word for blue with a distinctly green traffic light, how were they supposed to refer to it officially? And simply changing the light to blue instead of green went against a major worldwide push to standardize traffic signals. So in the early 1970s, Japan decided on a blue-green color sometimes known as “grue” or “bleen,” meaning it’s technically both. While today only some lights combine the colors, and others are clearly green, all of them are still “ao.”

How did this confusion over traffic light color happen?

Busy traffic at night in a Japanese city with a line of green lights visible

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Because many countries developed their own systems in relative isolation, concepts like color weren’t viewed similarly across the world, and many early cultures recognized only a few colors. For instance, old forms of the Japanese language only named four colors: blue, red, black, and white.

Even though modern Japan has dedicated words for green and blue, it’s not uncommon for objects to be called blue when they’re actually green. This habit has been ingrained in the culture and has Japanese speakers continuing to refer to anything blue or green as “ao.” For instance, a green Granny Smith apple is referred to as an “aoringo,” which starts with “ao,” meaning blue.

This phenomenon includes traffic lights, which were originally unmistakably green. Katsuhiro Ito, an expert in Japanese language and culture, explained to Reader’s Digest, “When traffic signals were first introduced to Japan [in the 1930s], the green light was sometimes called green … However, after World War II, the Road Traffic Act described the traffic light as ‘ao,’ and it has been referred to that way ever since.”

This isn’t the only unique twist that sets the country apart from others in terms of road management. The addition of several hand-painted traffic signs reduced Japan’s traffic accidents in a profound way.