The green light

Origin

Before the familiar red, yellow, and green, early traffic signals were quite different. In 1868, London installed a gas-powered signal with red and green lights, but it exploded, killing a policeman. The modern electric traffic light system, however, began to take shape in America in the early 20th century. By 1912, Salt Lake City had a manual red-green light, and Detroit followed in 1919 with the first three-color signal. These systems quickly standardized the meaning of 'green' as the signal to 'go' or 'proceed.' It wasn't long before this clear, universal directive from the street found its way into everyday language, transforming a simple traffic instruction into a powerful metaphor for permission and progress in any venture.