Why Japan's Traffic Lights Are Blue—A Hidden Debate Between Language, Law, and Light
The land of the rising sun blends history with cutting-edge technology, and car enthusiasts know Japan for its staggering variety of makes and models, each with its own cultural flair. Yet a quiet traffic-light quirk reveals a deeper story: some signals use a blue-green shade. A United Nations treaty on road signs and signals, signed by 35 countries in 1968 and now adopted by about 75 states, says green means go and red means stop. But neither the United States nor Japan signed that treaty, leaving Japan to navigate color law on its own. To resolve the dilemma—how to refer to a color when the Japanese word for blue and green used to be the same—the country adopted a blue-green shade in the 1970s, a compromise sometimes called grue or bleen. Officially, though, many lights are still labeled ao.
A Language Puzzle: ao, midori, and the Green Light
Historically, Japanese used the same word for blue and green: ao. Today green is midori, but many objects—like traffic signals—are still described with ao because of historical habit. When signals were first introduced to Japan in the 1930s, the green light was sometimes called green. After World War II, the Road Traffic Act described the signal as ao, and it has remained that way. In the early 1970s, Japan adopted a blue-green color for some signals to balance language and international standards; some sources call it grue or bleen, signaling both colors while still labeled ao. An everyday example: a green Granny Smith apple is called aoringo, a word that begins with ao, meaning blue.
A Practical Compromise: Some Lights Look Blue-Green, Others Green
The result is a practical compromise. Some signals skew blue-green, others appear clearly green, but the official label remains ao. The quirk isn’t merely linguistic; it reflects how cultures interpret color, history, and standards side by side. In addition to color quirks, the addition of hand-painted traffic signs reduced accidents in a profound way.
