Traffic Light Encyclopedia

There are two types of traffic lights. The ones shown to motor vehicles are called motor vehicle lights. They usually refer to signal lights that are composed of red, yellow, and green (green is blue and green) lights that are used to direct traffic.

When the green light is on, vehicles are allowed to pass, and when the yellow light is flashing, vehicles that have crossed the stop line can continue to pass; those who have not passed should slow down and stop before the stop line and wait. When the red light is on, vehicles are prohibited from passing. The pedestrian crossing lights that are shown to pedestrians usually refer to signal lights that are composed of red and green (green to blue and green) lights to direct traffic. Red lights stop and green lights go.

At the beginning of the 19th century, in York City in central England, red and green outfits represented the different identities of women. Among them, the woman in red indicates that I am married, while the woman in green is unmarried. Later, there were frequent incidents of horse-drawn carriages in front of the Houses of Parliament in London, so people were inspired by the red and green outfits. On December 10, 1868, the first member of the signal light family was born on the square of the Houses of Parliament in London. A lamp designed and manufactured by British machinist De Hart

The column is 7 meters high, and a red and green lantern is hung on the body-a gas traffic signal light. This is the first signal light on a city street. At the foot of the lamp, a policeman holding a long pole pulled the belt to change the color of the lantern as he wanted. Later, a gas lampshade was installed in the center of the signal light, and two red and green glasses were alternately shielded in front of it. Unfortunately, this 23-day-old gas lamp suddenly exploded and went out, killing a policeman on duty.

Since then, the city's traffic lights have been banned. It was not until 1914 that the city of Cleveland in the United States took the lead in restoring traffic lights, but at this time it was already an 'electrical signal light.' Later, in cities such as New York and Chicago, traffic lights reappeared one after another.

With the development of various vehicles and the needs of traffic command, the first veritable three-color light (red, yellow, and green) was born in 1918. It is a three-color circular four-sided projector installed on a high tower on the Fifth Street in New York City. Due to its birth, the city's traffic has been greatly improved.

The inventor of the yellow signal light is Hu Ruding of our country. With the ambition of 'saving the country by science', he went to the United States for further study and worked as an employee of General Electric Company of the United States where the inventor Edison was the chairman. One day, he was standing at a bustling intersection waiting for the green light signal. When he saw the red light and was about to pass, a turning car passed by with a cry, scaring him into a cold sweat. Back in the dormitory, he repeatedly pondered, and finally thought of adding a yellow signal light between the red and green lights to remind people of danger. His suggestion was immediately affirmed by relevant parties. Therefore, the red, yellow, and green three-color signal lights are a complete command signal family, spreading all over the world in the field of land, sea, and air transportation.

The earliest traffic light appeared in London, England in 1868. At that time, the traffic lights were only red and green. After improvement, a yellow light was added. The red light means stop, the yellow light means preparation, and the green light means passage. The earliest road traffic lights in China appeared in the British Concession in Shanghai in 1928.

From the earliest hand-held belt to the electrical control in the 1950s, from the use of computer control to modern electronic timing monitoring, traffic signal lights are constantly updated, developed and improved in scientific and automated aspects.

The traffic lights were invented by African American Garrett Morgan in 1923. Prior to this, railway traffic has been using automatically converted light signals for some time. However, because the train runs in a single train according to a fixed timetable, and it is not easy for the train to stop, the signal used on the railway has only one command: pass. The traffic lights of road traffic are different. To a large extent, its duty is to tell the driver to stop the vehicle.

No one driving a car wants to see the stop signal. James, a psychologist at the University of Hawaii in the United States, points out that people have a tendency to associate brakes and accelerators with self-esteem. He said: When the driver sees the yellow light, he secretly prepares to accelerate. If the red light turns on at this time, a feeling of disappointment will immediately occur. He called the intersection a 'psychological power zone.' If his theory is valid, this area should belong to the category of superego (supere go) rather than instinct (id) in Freudian psychological theory.

The new traffic lights can take photos of people who run through the red lights. The offending driver will soon receive a fine. Some traffic lights also have the function of monitoring the speed of the vehicle.

In fact, the use of these three colors as communication signals is related to the structure of human visual functions and psychological responses.

Our retina contains rod-shaped and three cone-shaped photoreceptor cells. The rod-shaped cells are particularly sensitive to yellow light, and the three types of cone-shaped cells are the most sensitive to red light, green light, and blue light, respectively. Because of this visual structure, it is easiest for people to distinguish between red and green. Although yellow and blue are easy to distinguish, because the eyeball has fewer photoreceptor cells that are sensitive to blue light, red and green are better to distinguish colors. So, what color the traffic light uses is also asked by the university!

Color also implies activity. To express heat or intensity, red is the strongest, followed by yellow. Green has the meaning of colder and calmer. Therefore, people often use red for danger, yellow for alertness, and green for safety.

Moreover, because red light has the strongest penetrating power, other colors of light are easily scattered and are not easy to see in a foggy day, and red light is the least likely to be scattered, even if the air visibility is relatively low, it is easy to be seen. There will be no accidents. So we use red to indicate prohibition.


According to Order 123, 6 points for violating road traffic lights, including running red and yellow lights. The yellow light was originally a warning to the driver and a buffer for the traffic. The reason for the current regulations is that there have been many traffic accidents in the yellow light time zone. The root cause of the accident was the lack of necessary traffic safety awareness, and even turned the yellow light that was originally a warning light into an 'acceleration warning light.'

According to international practice, you should stop when the yellow light is on. Failure to stop is a violation of regulations. If any part of the car body has passed the line when the yellow light is on, you can continue to drive past. If you do not cross the line, you should brake to stop, even if you cross the zebra crossing, you must stop. As long as you stop, you will not be punished.