1858, red and blue mechanical wrench signal lights with gas as light source were installed on the main streets of London, England, to direct the passage of carriages. This is the earliest traffic light in the world.
1868, British mechanical engineer knight installed the world's earliest gas traffic lights in the square in front of Westminster Parliament Building in London. It consists of red and green lanterns and rotating square glass. Red means "stop" and green means "pay attention". On the 23rd day of its operation, the gas lamp suddenly exploded, and a policeman on duty died on the spot, so it was cancelled.
19 14, electric traffic lights appeared in the United States. This traffic light consists of red, green and yellow circular projectors, which are installed on a tower on Fifth Avenue in new york. The red light means "stop" and the green light means "pass".
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With the development of various means of transportation and the need of traffic command, 19 18 gave birth to the first true tricolor lamp (red, yellow, green). It is a three-color circular four-sided projector, which is installed on a tower on Fifth Street in new york. Because of its birth, urban traffic has been greatly improved.
The inventor of the yellow signal lamp is Hu Ruding in China. With the ambition of "saving the country through science", he went to the United States for further study and worked as a clerk in the American General Electric Company with Edison as its chairman. One day, he stood at a busy intersection waiting for the green light signal. When he saw that the red light was about to pass, a turning car roared past, which scared him into a cold sweat.
Back in the dormitory, he pondered it over and over again, and finally thought of adding a yellow signal light between the traffic lights to remind people of the danger. His suggestion was immediately affirmed by relevant parties. Therefore, in the field of land, sea and air transportation, red, yellow and green signal lights have spread all over the world as a complete command signal family.
The earliest traffic lights on the road in China appeared in the British Concession in 1928. From the earliest handheld to the electrical automation control in 1950s, from computer control to modern electronic timing monitoring, traffic lights are constantly updated, developed and improved in science and automation.
Baidu encyclopedia-traffic lights
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