By Adam K. Raymond 

You likely spend a lot of time whizzing by or stopped at traffic lights. But how much do you know about them?


No matter where you are in the world, the rule is the same: Red means stop, and green means go. The custom dates back to 1848, when British steam ships began displaying lights on the sides of their vessels to prevent them from crashing into each other at night. The light on the right side was green, and the one on the left was red. If your boat approached another vessel from the right, you could pass, but if you approached on the left, you had to give way. By the mid-1800s, transportation authorities in the United States were using the same system for railways. Then they applied it to roads, and red and green lights have commanded traffic ever since.

While the system is fairly universal today, the Chinese did take a stab at improving it back in the 1960s. During the Cultural Revolution, members of the Red Guard began publicly voicing their displeasure with red stoplights. Because red was the color of the revolution, they felt it should mean “go,” symbolically encouraging the spread of Communism. The movement to swap the meaning of red and green lights gained momentum until Zhou Enlai, the Premier of the Republic, convinced the Red Guard that it was, in fact, a horrible idea.


According to the late Dutch traffic specialist Hans Monderman, the best way to make intersections safer is to ditch traffic lights altogether. His philosophy is simple: If no one is ever automatically given the right-of-way, then everyone will be more cautious. Monderman calls his theory Shared Spaces, and it’s taken hold in some small European cities, including the Dutch town of Drachten. Beginning in 2005, the city removed all but a few of its traffic lights, forcing its roughly 50,000 residents to drive more carefully and more considerately. Prior to the change, one major intersection in Drachten averaged about nine accidents per year; these days, that number is down to one.


Ever wonder how colorblind drivers read traffic lights? Most rely on the order of the lights. (Green is on bottom; red is on top.) But when the lights are dim or there’s heavy fog, it’s difficult to know which light is illuminated. One solution to this problem involves adding hints of orange to the red light and hints of blue to the green light, making them more distinguishable to most colorblind drivers. Another idea, called Uni-Signal, makes it possible to distinguish the lights by shape. A triangle is used for the red light, a square for the green light, and a circle for the yellow light. By using shapes, colorblind drivers can recognize traffic lights from much farther away.

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