Traffic light colors

Originally, traffic lights only had red and green. Later, after improvements, a yellow light was added. Red means stop, yellow means prepare, and green means go. The use of these three colors as traffic signals is related to human visual structure and psychological responses.

 

The human retina contains rod cells and three types of cone cells. Rod cells are particularly sensitive to yellow light, while the three types of cone cells are most sensitive to red, green, and blue light, respectively. Due to this visual structure, humans can most easily distinguish red and green. Although yellow and blue are also easily distinguishable, the eye has fewer photoreceptor cells sensitive to blue light, so red and green are still the best for color perception.

 

Traffic lights are not randomly placed

Scientific Basis: According to optical principles, red light has a long wavelength, strong air penetration ability, and is more noticeable than other signals. Therefore, green is used as a stop signal because the difference between red and green is the greatest, making them easy to distinguish (red-green color blindness is a minority). In addition, colors can also convey specific meanings. Red is the strongest color to express heat or intensity, followed by yellow. Green, on the other hand, carries connotations of coolness and calmness. Therefore, people often use red to represent danger, yellow to represent warning, and green to represent safety.