At the beginning of the 19th century, the red and green dress represented the different identities of women in the central British city of York. Among them, the attire woman said I was married, and the green woman is unmarried. Later, the London Parliament building often happened in front of the carriage rolling people's accident, so people were inspired by the red and green, December 10, 1868, the first member of the Semaphore family was born in the square of the London Parliament building, by the time the British machinist De Hart Design, manufacture of the lamp post 7 meters high, hung with a red, Green Two-color lantern-Gas traffic lights, this is the city street's first signal light. At the foot of the lamp, a policeman with a long pole would arbitrarily affect the color of the belt-changing lantern. Later, in the center of the signal lamp installed gas lampshade, its front has two red, green glass alternating occlusion. Unfortunately, the 23-day-late explosion of a gas lamp suddenly blew out and killed a policeman on duty.
Since then, the city's traffic lights have been banned. It was not until 1914 that Cleveland in the United States took the lead in restoring the traffic lights, but it was already an "electrical beacon". Later in cities such as New York and Chicago, traffic lights came back in.