157 years ago today, on December 10, 1868 (October 27, 1868 in the lunar calendar), the world's first traffic signal was born in the UK. In the early 19th century, in York City in central England, red and green clothes represented different identities of women respectively. Among them, the woman in red said that I was married, while the woman in green was unmarried. Later, carriages and carriages often ran over people in front of the Houses of Parliament in London, England, so people were inspired by red and green clothes. On December 10, 1868, the first member of the signal family was born in the square of the Houses of Parliament in London. The lamp post designed and manufactured by the British Mechanical Teacher Hart at that time was 7 meters high and was hung with a red and green lantern-a gas traffic signal. This was the first signal light on the city's streets. At the foot of the lamp, a policeman holding a long pole pulled the belt to change the color of the lantern at will. Later, a gas lampshade was installed in the center of the signal light, with two pieces of red and green glass alternately blocking the front. Unfortunately, the gas lamp that had only been in existence for 23 days suddenly exploded and killed itself, killing a policeman on duty. Since then, traffic lights in the city have been banned. It was not until 1914 that Cleveland in the United States was the first to restore traffic lights, but by this time it was already an "electrical signal." The first truly three-color lamp (red, yellow and green symbols) was born in 1918. It is a three-color circular four-sided projector installed on a tower on Fifth Street in New York City. The inventor of the yellow signal light was Hu Ruding of our country. He went to the United States for further study with the ambition of "saving the country through science" and served as a member of General Electric Company of the United States, where the great inventor Edison is chairman. One day, he stood at a busy intersection waiting for the green light signal. When he saw the red light and was about to pass by, a turning car passed by with a whoosh, which scared him into a cold sweat. Back in the dormitory, he thought about it repeatedly and finally thought of adding a yellow signal light between the red and green lights to remind people of danger. His suggestion was immediately confirmed by relevant parties. As a result, red, yellow and green signal lights form a complete command signal family and spread throughout the world's land, sea and air transportation fields.