Why Does Red Mean “Stop” and Green Mean “Go”? The History of Stoplights

Traffic light showing red, green, and yellow colors along with street lamp post. (Ellen van Bodegom/Getty Images)

Everyone, even small children, seems to intuitively know that the color red means “stop” and green means “go.” Today, we may take stoplights for granted—or curse them for slowing us down—but stoplights were an important invention, forever linking these colors with movement.

The First Stoplights

Shortly after the first automobile, there was the first automobile accident. As a preventative measure, many cities and larger towns erected traffic towers at busy intersections, but they were hilariously rudimentary compared to modern stoplights, with traffic officers manually signaling oncoming traffic by flashing different colored lights. It soon became clear that traffic rules needed to be standardized so that drivers would always know which color meant “stop” and which color meant “go," and when picking the colors, traffic officials took a cue from the railroads, which originally featured white lights for "go," green lights for "caution," and yellow lights for "stop" but by that time had adopted the modern color maxim after falling lenses proved the disaster of using white lights for "go." Red just didn't have a "go" feel to it, being the color of blood and panic, so the whole scheme was redone.