The importance of traffic lights to traffic safety is self-evident. When the red light stops at the green light, the traffic light is also commonly known as the "traffic light".
The birth of traffic lights can be traced back to the beginning of19th century. In York City in the middle of England, women wear red and green clothes to distinguish their identities: red clothes represent married and green clothes represent unmarried. At that time, due to frequent car accidents in front of Westminster Parliament Building in London, England, inspired by women's red and green clothes, British railway signal engineer J.P.Knight put forward the idea of designing red and green traffic signals.
The idea soon came true. 1868 12 10, the first member of the signal lamp family was born in London Parliament Square. This signal lamp is a gas lamp. The lamppost is 7 meters high and there are two lanterns hanging on the top, one red and one green.
This kind of gas traffic light needs manual operation. The center of the signal lamp is equipped with a gas lampshade, which is alternately shielded by two red and green glasses. The police on duty need to pull the belt to change the lights of different colors. However, the first gas traffic light exploded more than 20 days later, and the police on duty that day were killed and the traffic lights were banned.
It was not until 19 14 that the traffic lights in Cleveland, Ohio reappeared. 1965438+On August 5, 2004, the American Traffic Light Company improved the invention of Lester Will, a police officer in Salt Lake City, and made a set of power signal system, which is the first set of power signal system put into use in human history. The first electronic signal light was placed at the intersection of Euclid Avenue East 105 Street in Cleveland. Only red and green, the buzzer will warn you before the light is turned on. Subsequently, new york, Chicago and other American cities also adopted the traffic lights.
Red, green and yellow are the most suitable colors for signal warning.
How did the red and green signal lights become the familiar red and green Huang San signal lights? There is a saying by Hu Ruding, a native of China. Hu Ruding studied at Cornell University and Massachusetts Institute of Technology in his early years. 1925, he studied in a class jointly organized by General Electric Company and Massachusetts Institute of Technology, and Edison was the chairman of this class. He is a student of Edison.
When Hu Ruding worked for General Electric Company, he used to wait for the green light at the intersection. When the green light was about to light, a car drove by quickly. In addition to palpitations, he also thought of adding a yellow signal light in the middle of the traffic lights. This proposal has also been affirmed and supported by the U.S. government, and yellow signal lights have also been popularized around the world.
However, this statement is not very reliable, because as early as 19 18, the first red, yellow and green light appeared in new york-a three-color circular four-sided projector installed in a tall building on Fifth Avenue in new york. 1920, WilliamPotts, a police officer in Detroit, USA, also invented a patented three-color four-way yellow light signal lamp. Since then, yellow lights have appeared in many invention patents of traffic lights. What is certain, however, is that Hu Ruding did vigorously promote the three-color signal lamp.
Red, green and yellow are the most suitable colors for early warning signals, which are related to people's visual structure and psychological reaction. The human retina contains rod-shaped and cone-shaped photoreceptor cells. Rod cells are particularly sensitive to yellow light, while three cone cells are most sensitive to red light, green light and blue light, respectively. Therefore, it is the easiest for humans to distinguish between red and green. Although yellow and blue are easy to distinguish, red and green are the first choice because there are fewer photosensitive cells in the eyeball that are sensitive to blue light. From the psychological reaction, the strongest feeling is red, followed by yellow, and green is a cool color with calming effect. So people are used to using red for prohibition, yellow for warning and green for safety.
1968 The United Nations Agreement on Road Traffic and Road Signs and Signals stipulates the meanings of various color signal lights. Among them, the yellow light is a warning signal. Vehicles facing the yellow light cannot cross the stop line, but when the vehicle is too close to the stop line to stop safely, it can enter the intersection. Since then, this provision has been widely applied all over the world.
1940, traffic kiosks and traffic police on the streets of Shanghai Concession.
The earliest traffic lights in China appeared in the British Concession. According to some data, in 1923, Shanghai Concession began to use mechanical devices to direct vehicles to stop at some intersections. In April 13 of the same year, two red and green traffic lights were installed on Nanjing Road in Shanghai.
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