Traffic signals are signals that direct the operation of traffic, generally consisting of red, green and yellow lights, as silent "traffic police", they play a great role in the management and control of road traffic. However, did you know that the original signal lights are only red and green colors? Today, I will introduce you to the origin and development of traffic signals.

First, the origin of traffic signals

The origin of red and green lights can be traced back to the early 19th century in the United Kingdom. At that time, some European countries, including the United Kingdom, have been popular carriage, but there is no guidance for pedestrians and carriages to pass the signal indication equipment, so whether in the mountain paths or the city center of the busy avenue, carriage accidents often occur, which not only caused harm to the safety of pedestrians, but also often cause traffic chaos, congestion.

At that time in the city of York in central England, women's dress is not arbitrary, red, green two colors represent the different identities of women. In 1866, J. P. Knight, a British railroad signal engineer, was inspired by the red and green colors of women's dress and came up with the idea of designing traffic signals with red and green colors, which was soon put into practice and the traffic signals were gradually created.

On December 10, 1868, the first traffic signal in history appeared in front of the Parliament building in Westminster, England, this traffic signal is about 7 meters high, in its top hanging red and green rotatable gas lanterns, in order to switch the red and green lanterns, under this light must stand a police officer holding a long pole, through the belt pulling the lantern to switch colors, later also in the In the middle of the signal light, red and green shades were added, with red and green glass alternating in front to cover, without lighting the gas lamp during the day, only the switching of red and green shades to guide people forward or stop, and at night the gas lamp was lit to illuminate the red and green shades.

In addition, the traffic police also need to decide the time to change the signal according to the prevailing road conditions, and use the method of blowing the whistle to remind pedestrians and vehicles that the signal is about to change. At first the British government did not believe that this method can work, they think that either pedestrians or vehicles, will not stop because of this look a bit like a decorative signal, but the role played by the signal to their surprise, many people will follow the instructions of the signal consciously stop or pass, the number of carriage accidents also dropped significantly.

However, the good times did not last long, on January 2, 1869, only 23 days after the birth of the first traffic signal will suddenly explode and destroyed, and was responsible for the red and green color switch police officers killed. In view of this situation, the British government immediately stopped the use of this signal, but this only 23 days of life of the signal but ignited the whole Europe and the whole world to develop the passion of traffic lights, and soon after, all kinds of traffic lights will be like a spring.

As horse-drawn carriages were gradually replaced by automobiles, the need for effective traffic signals became urgent, and in 1914, the city of Cleveland in the United States was the first to restore traffic lights. In the "post-gas signal" era, some European countries began to install police officers on the roads and reversible signs, most of which were about 2 meters high and had signs that said "GO" and "STOP". Most of these signs are about 2 meters high and have signs with "GO" and "STOP" written on them, and the police officers on duty are responsible for turning them over at regular intervals, while pedestrians and vehicles move forward or stop according to the meaning of the words on the signs.

Second, the improvement and development of traffic signal

01 From hand crank to electric control

With the gradual completion of the second industrial revolution, the hand-cranked traffic signal, which relies solely on traffic police, revealed many shortcomings in the actual use of the process. This greatly limits the scope of its application. At the same time, with the birth of the first internal combustion engine automobile, horse-drawn carriages were gradually replaced by faster and easier-to-use automobiles, at which time the use of standardized and effective traffic signals became an urgent problem.

In 1912, a police officer named Lester Wire in Salt Lake City invented the first electric traffic signal, which still used the colors red and green, and the color was not chosen based on the woman's name. This time, the basis for the choice of color is not the difference in women's dress, but the full consideration of the qualities of different colors of light, as well as people's reception and response to different colors. Because of the long wavelength of red light, the ability to penetrate the air is very strong, so it is easier to attract people's attention than other colors of the signal, while green and red are complementary colors, the contrast between each other is obvious, easy for pedestrians and drivers to identify.

On August 5, 1914, the American Traffic Signal Company improved upon the traffic signal invented by Lester Wire and installed a buzzer on top. The company placed it at the intersection of East 105th Street at Euclid Avenue in Cleveland, Ohio. The traffic signal was lit by electricity, and the police officers were required to control the switching of the signal in the booths set up around the signal, and if necessary, the length of the signal switching time could be controlled according to the actual traffic conditions at the intersection. Before the signal is switched, the buzzer will alarm first to remind people that the color of the signal is about to change, so it is evident that this sense of "leaving time to prepare" has been produced as early as when the first electric signals appeared.

02 from electric control to self-control

In the early 1920s, many areas of the United States began to upgrade traffic signals on this basis to varying degrees, in 1917, the first interrelated traffic signal system appeared on the streets of Salt Lake City, the Americans set up electric traffic signals at the intersection of six streets, and they are connected to each other, by a post in the police officer unified control of color conversion. Houston, Texas, USA also popularized interconnected traffic signals and installed a four-sided, three-light traffic signal system in the center of some intersections.

In the following decades, due to technical constraints, the switching of traffic signals has been manually controlled, but with the birth of the first transistor in 1947 and the first integrated circuit board in 1958, human breakthroughs and advances in information technology have also provided the conditions for the complete automation of traffic signals.

In 1963, the first automatically controllable signal appeared on the streets of Toronto, Canada. The signal was controlled by a computer chip for traffic signals, while an automatic control system contained traffic signals at multiple intersections, and all signal transitions were controlled by the computer, and the police officers only needed to monitor uniformly at designated locations, which greatly reduced the pressure on the traffic police officers.

Subsequently, the development of traffic lights slowed down until the 1970s when Microsoft was established and rapidly rose in the world, traffic signals had a unified processing system, since then traffic signals mostly use the system provided by Microsoft for logical switching control between red, yellow and green, completely saying goodbye to the era of manual control.

03 Origin of the yellow light

At the beginning of the creation of the signal is only red and green two light colors, about the origin of the traffic signal yellow light world recognized there are two sayings, the following will be introduced one by one.

① According to legend, in 1920, a police officer named William Potts in Detroit, Michigan, United States, based on the traffic signals at the time again improved, developed a four-sided three-light multifunctional traffic signal, this signal is divided into four sides, each side are vertically arranged three lights, when its arrangement and function has been similar to the signal we now know. The red and green lights indicate stop and pass, while the yellow light indicates "caution".

Another story is that a Chinese named Hu Ruding also came up with a similar idea and put it into practice. One day in 1927, he was waiting for a green light at an intersection on a busy street, and when he saw the light come on and was about to pass, a car almost brushed his body and sped by, frightened. Hu Ruding began to think about how to solve the problem of switching between red and green lights to warn.

After some thoughtful consideration, Hu Rueding cleverly thought of adding a yellow signal between the red and green lights, and arranged in the order of red, yellow and green from top to bottom, to remind people that the signal is about to switch, different driving directions of pedestrians or vehicles to prepare accordingly. Once this proposal was put forward it received the affirmation and support of the U.S. government, who not only added the relevant provisions in the traffic regulations, but also extended the red, yellow and green traffic signals to the world.

Considering that the yellow signal was introduced in the U.S. as early as 1920 to remind people to pay attention to the signal switch, it is still debatable whether this discovery of Ruding Hu can be considered as the invention of the yellow light, but this Chinese boy, who was only in his early 20s at that time, undoubtedly contributed his share to the development of traffic signals.

As an important part of urban traffic management and control, traffic signals have been changing and improving along with the development of urban traffic. Understanding the history of traffic signal development can bring us more meaningful thinking, so as to improve our own traffic literacy and sentiment, and better strive for the construction of a modern, intelligent and digital urban traffic control system.