Traffic lights consist of red, green, and yellow lights. The red light indicates that the passage is forbidden, the green light indicates that the passage is permitted, and the yellow light indicates the warning.

In 1858, red and blue mechanical wrench-type traffic lights were installed on the main streets of London, England, to direct the carriages. This is the oldest traffic signal in the world. In 1868, British mechanical engineer Neutt installed the earliest gas-powered traffic light in the square in front of the parliament building in Westminster, London. It is composed of red and green two-revolving square glass lanterns, red means 'stop' and green means 'note'. Just on the 23rd day of its operation, the gas lamp suddenly exploded. A police officer on duty was killed on the spot and was removed.
In 1914, an electric start-up traffic light appeared in the United States. This traffic light consists of a red, green, and yellow light projector that is mounted on a high tower on 5th Street in New York City. The red light means 'stop', and the green light means 'pass'.
In 1918, there were traffic lights and infrared traffic lights with control. With the control of traffic lights, one is to put the pressure detector in the ground, the vehicle will turn green when it is close to the red light; the other is to use a loudspeaker to start the traffic lights, when the company presses the bull's-eye with a red light, it will make The red light turns green. Infrared traffic lights When a pedestrian steps on a pressure-sensitive surface, it can detect that someone is crossing the road. The infrared beam can extend the red light of the signal lamp for a period of time and delay the release of the car to avoid traffic accidents.
The appearance of traffic lights has enabled traffic to be effectively regulated. This has a significant effect on diverting traffic flow, improving road capacity and reducing traffic accidents. In 1968, the UN Agreement on Road Traffic and Road Signs stipulated the meaning of various signals. The green light is a traffic signal. Vehicles facing the green light can go straight, turn left and turn right, unless another sign prohibits a certain kind of steering. Right-turning vehicles must give priority to pedestrians who are legally driving at intersections and crossing pedestrian crossings. The red light is a forbidden signal. Vehicles facing the red light must stop behind the parking line at the intersection. The yellow light is a warning signal. Vehicles facing the yellow light cannot cross the parking line, but vehicles can approach the intersection when they are very close to the parking line and cannot safely stop. Since then, this provision has begun to be universal in the world.

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