raffic police have been around for as long as there's been traffic. Even in the horse-and-buggy days, roads became so crowded there was a decided need for law and order; police departments organized groups of officers whose sole responsibility was to maintain order on the highways and byways. The advent of the automobile intensified the need for traffic police; as technology improved and automated traffic signals came into play, traffic police officers spent less time making sure traffic kept moving and more time crafting and enforcing laws designed to prevent accidents---from making drivers wear seatbelts to cracking down on speeders and other reckless drivers.
The origins of modern traffic police can be traced to London, England, in the 1800s. Horse-drawn traffic became so congested that police took to busy intersections with whistles and a flurry of waving arms and hand signals. The problem was, they often couldn't be seen, particularly at night. To increase their visibility, they began carrying gas lights with colored lens. A green light meant go; a red light, stop.