Traffic Lights Predate Cars

Long before the roar of engines filled city streets, the clatter of horse (Review)-drawn carriages and throngs of pedestrians created their own brand of gridlock in Victorian London. To bring order to the chaos near the Houses of Parliament, railway signal engineer J.P. Knight adapted the technology he knew best. In 1868, he installed a towering signal that used semaphore arms, much like those on a railway line, to direct traffic during the day. For nighttime visibility, it was equipped with red and green lamps illuminated by flammable gas.

This pioneering device was not automated; a police constable was required to stand beside it and operate the arms and lights manually. Unfortunately, this early experiment in traffic control was both short-lived and dangerous. Just weeks into its operation, a leak in a gas line caused the signal to explode, severely injuring the police officer on duty. The dramatic failure put a halt to the concept for decades, and it wasn't until the rise of the automobile in the early 20th century that the need for a safer, electric version of the traffic light became undeniably urgent.