Why do headlights have yellow light?
3 Answers
Because yellow light has strong penetration, the actual power of general headlights needs to be 5w, above 1000 lumens, and yellow light between 3000k and 4200k is recommended. Here is some extended information about car headlights: Function: The function of car headlights is to provide illumination for night driving. Car headlights are also known as car front lights or car LED daytime running lights. As the eyes of a car, they not only relate to the external image of a car owner but are also closely linked to safe driving at night or under bad weather conditions. Types: Car lights can be divided into two types by purpose: lighting and auxiliary. Among them, only the headlights and some fog lights equipped on cars serve the purpose of lighting, while the rest are auxiliary lights.
I've been driving for over 20 years, and using yellow headlights is mainly for safety reasons. Older cars used halogen bulbs, which naturally produced yellow light without filters, offering excellent penetration. I remember driving at night during a heavy rainstorm - my white headlights created a blurry view, while the truck next to me with yellow fog lights illuminated the road much more clearly. Nowadays most cars use white LED lights, but yellow light remains effective in foggy conditions due to its longer wavelength, which scatters less when hitting water vapor and thus illuminates further. France once mandated yellow headlights precisely because of their superior safety data. Some car enthusiasts in the modification community intentionally apply yellow films, pursuing both a retro look and improved visibility in rainy or foggy weather.
Anyone in automotive design knows that yellow light selection is the result of comprehensive considerations. With wavelengths ranging from 570 to 590 nanometers, its spectral distribution resembles sunlight after passing through the atmosphere, making it highly acceptable to the human eye. In the early days, halogen bulbs were cost-effective and long-lasting, naturally popularizing yellow light. Later, regulations promoted safer light colors, reinforcing yellow light's advantage in penetrating haze, especially when paired with reflector bowl structures, achieving decent efficiency. Modern LEDs can simulate various light colors, but high-end models still use yellow fog lights because actual tests show their scattering rate is about 20% lower than white light. From a traffic engineering perspective, yellow light also offers more prominent visibility in mixed traffic flows.
