Yellow headlights, what is the purpose?

BMW E30 frenched headlights

Commonly, European cars from the 1930's through the 1990's feature yellow tinted headlights. It is even more common to see cars of all generations, even present day, with yellow fog lamps. Is this purely a cosmetic feature or is there a practical application for this? The answer is that yellow tinted headlights have a purpose of safety.

What is the purpose of a yellow tinted headlight design?

The purpose of having yellow tinted headlights is to improve visibility at night by removing blue to violet colors from the wavelength spectrum.

What is the science behind yellow headlights?

On the color spectrum yellow light has a longer wavelength than blue to violet colors. The shorter the wavelength the harder it is for the human eye to see. When looking at the wavelength chart shown below, you can see yellow to red colors are ideal for seeing at night. In inclement weather, having a blue or white light shining on rain, fog or snow can cause a glaring effect thus reducing visibility. Yellow light does not reflect off water as easily as blue thus it can allow the driver to see the road more clearly.

light spectrum

What is the history behind yellow headlights?

Now that we know the science behind why yellow light is better than blue or white in night time driving conditions let us learn the history of yellow tinted headlights are called “French” lights.  In 1936 the French government passed a law stating all vehicles produced from 1937 onward must have yellow headlights.

Although the main purpose was for safety, some say this was also a way for the French government to easily discern a French car from a foreign car while driving at night.  This was important during World War II in the 1940’s.  By 1993, the European Unionc forced France to conform to their standards of safety, thus the going away of the yellow tinted headlights in exchange for compliance of using white headlights.  If a French car was first registered prior to 1993 you are able to still have yellow headlights.

How can I get yellow tinted headlights?

The easiest way to convert your existing clear headlights to yellow is by applying a yellow vinyl film over them. Although visibility in inclimate weather conditions will be improved drivers will see about a 12% loss in brightness. A benefit of this modification is that the process is completely reversible if you do not like the look.

Why does BMW use orange interior lighting at night?

If you want to learn why BMW uses orange interior night light you can read our blog post on this topic HERE.

How do BMW laser light headlights work?

If you want to learn how BMW laserlight headlight technology works click HERE.

Check out an Old Top Gear video from 1990 explaining the French headlights further.

Article written by: Greggor Moar - February 05, 2020

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BMW E30 yellow headlights

Photo Credit: Greggor Moar

BMW E30 yellow headlights

Photo Credit: Greggor Moar

BMW E30 yellow headlights

Photo Credit: Greggor Moar