What do the red, yellow and green lights stand for?

The legal meaning of yellow traffic light is "warning", that is, "warning" and "vigilance". According to the Road Traffic Safety Law and its implementing regulations, the function of the yellow light signal is to clear the intersection, so that vehicles that have crossed the stop line can pass quickly during the yellow light period. In other words, the yellow light plays an early warning and buffering role. At first, there were only two colors, red and green. Later, after improvement, yellow light was added, red light means stop, yellow light means preparation, and green light means passage. Using these three colors as traffic signals is also related to people's visual structure and psychological reaction.

Development history

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".

19 18, traffic lights with control and infrared traffic lights appeared again. There are controlled traffic lights, one is to put the pressure detector underground, and the vehicle will turn green as soon as it approaches the red light; The other is to start the traffic lights with a loudspeaker. When the driver meets a red light, he presses the buzzer to turn the red light into a green light. Infrared traffic lights when pedestrians step on the pressure-sensitive road, they can detect that someone is crossing the road. Infrared beam can prolong the red light of traffic lights for a period of time, delay the release of cars and avoid traffic accidents.

Pedestrian crossing signal lamp

A set of signal lights consisting of red pedestrian standing mode and green pedestrian walking mode guide pedestrians to pass.

When the green light is on, pedestrians can cross the crosswalk.

When the red light is on, pedestrians are prohibited from entering the crosswalk, but those who have already entered the crosswalk can continue to pass or wait at the center line of the road.