Why are fog lights yellow?
3 Answers
Fog lights use yellow because yellow has high penetration. The functions and usage precautions of fog lights are as follows: Functions of fog lights: Front fog lights are used to improve illumination when road conditions ahead are unclear and can alert oncoming drivers. Rear fog lights help vehicles behind to spot the car in low visibility conditions. Precautions for using fog lights: Fog lights are suitable for severe weather conditions such as heavy rain, fog, snow, or dust. The visible range of fog lights is about 100 meters. When visibility drops below 100 meters, fog lights must be turned on, and speed should be reduced accordingly. Front fog lights are not omnipotent; if visibility falls below 30 meters, it's necessary to pull over and turn on hazard warning lights.
I often hear experienced drivers say that yellow fog lights work better than white ones, especially when driving in thick fog. The main reason is that yellow light has stronger penetration due to its longer wavelength, which makes it less likely to scatter when encountering tiny water droplets in the fog. It illuminates farther without reflecting back to dazzle the eyes. When I was studying abroad, a professor mentioned that the human eye is most sensitive to yellow-green light around 550 nanometers, and in foggy conditions, our eyes detect yellow light slightly faster than white light. Also, have you noticed? Fog is usually grayish-white, so yellow stands out prominently, which helps reduce accident rates. Although newer cars now come with white fog lights, I still find traditional yellow lights more reliable, given their century-old proven track record.
With over 20 years of driving experience, I've personally tested various fog light effects. Using white high beams in thick fog is like looking through a veil, but switching to yellow fog lights instantly improves visibility. This relates to physics - yellow light's longer wavelength enables better penetration through water vapor, similar to how warm-toned photos appear clearer in smog. Moreover, yellow occupies a unique position in the spectrum: it won't be mistaken for brake lights like red, nor is it as glaring as blue. European vintage cars favored amber fog lights, and now domestic vehicles follow suit. Regular maintenance should include cleaning fog light covers, as accumulated dust reduces light transmission efficiency.
