Simon Says

Before there were traffic signals there was heavy traffic, often chaotic, and in big cities policemen were placed at busy intersections to try and keep things sorted out. William Potts came up with the first traffic light in 1920, in Detroit, by adapting railroad signals. But the first traffic control device, gas powered, predated cars. It was put to use in London in 1868 to regulate the movement of horses, buggies, and swarms of pedestrians. It required a policeman to stand beneath it and turn it manually, and a year later it blew up, injuring it's operator. Overworked, no doubt. Traffic lights have been trying to get back at us ever since.