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Colored Headlights - Illegal

Being an automotive lighting and signalling researcher and consultant, I am very dismayed to see the increasing--and increasingly tolerated--use of blue-tinted bulbs in conventional headlamps. These are not the High Intensity Discharge (or "Arc Discharge") headlamps found on some high-end cars (Mercedes, BMW, Porsche, Audi, and Lincoln are the only companies to offer these arc-discharge lamps at the present, and only on certain models as a multi-thousand-dollar option).

I suspect the reason why drivers who illegally use these bulbs aren't being stopped is because traffic LEOs may not be aware of the extreme danger that they pose both to the driver of the car equipped with these non-approved bulbs and to all other road users; the purpose of this message is to try to get some information out to the LEO community in the hope that it will empower all of you to make our highways a little bit safer.


Various companies and individuals are selling halogen bulbs that have a coating that makes them light up with a bluish color. I receive at *least* four inquiries about these things per week. At least three of those four are from users who are angry because they installed them and not only cannot see properly, but in some cases have also been ticketed.

A typical such complaint (with my response) is reprinted below.


Halogen headlamp bulbs produce *very* little light in the blue frequency range. These blue bulbs have a filter coating on them that allows ONLY the blue frequencies through the filter. Because very little light is produced by a halogen bulb in this range in the first place, it is only this very small amount--a tiny fraction of the total amount of light produced by a halogen bulb filament--that ever reaches the road.

Headlamp illumination of the roadway and road hazards (including pedestrians, cyclists, animals, other cars, etc.) is dramatically reduced for the driver of a car equipped with blue headlamp bulbs.

Perversely, glare for oncoming traffic is sharply INCREASED when the driver must look at headlamps that have been equipped with the illegal blue bulbs. Why?

Blue is the shortest wavelength/highest frequency color of visible light, and, as such, scatters the most readily. (To prove this to yourself, find a dark blue storefront sign or something else that's a dark, pure blue against a dark background in the absence of white light. From any appreciable distance, it's almost impossible for your eyes to see the blue lighted object as a sharply defined form...the edges blur significantly.) When blue light strikes water (rain, fog, snow) it scatters in all directions and makes on-road vision very difficult.

Blue also is a very difficult color of light to look at if it is at all stimulates the reaction we call "glare".


There are several reasons I have learned by talking to users of these bulbs:

1) Because they have been confused by marketing claims for the blue bulbs which falsely and incorrectly equate the blue bulbs' performance with the very expensive arc-discharge headlamps found on top-line luxury cars. They have been led to believe that by replacing their car's proper headlamp bulbs with the blue-coated bulbs, their headlamps' performance
will be increased. In fact, quite the opposite is true; their headlamps' performance is dangerously DECREASED.

The placebo effect is alive and well, however, and the motorist who pays $45 for a set of these bulbs often will continue to insist that his headlamps have been made "better". Several such motorists have continued to insist that the blue bulbs' performance was better, even when the dangerously low actual light values were shown to them on a light meter, compared to the readings from proper non-blue bulbs.

2) Because they believe that the blue light makes their car look "cool". This would fall into the same category as the dark plastic headlamp and taillamp covers that are favored particularly by the younger male drivers for their appearance "enhancement" value, despite the fact that these covers, like the blue bulbs, are illegal and dangerous.


One clue is the type of car. As mentioned at the top of this message, there are only very few models at this time in North America being offered
with the arc-discharge headlamp system, and all of them are very top-end/luxury models from Audi, BMW, Lincoln, Mercedes, and BMW. If you spot bluish light coming from the front of a Honda or Chevy, you have found the illegal bulbs!

Another way to tell at-a-glance is to observe the color of the light. Genuine arc-discharge headlamps run with a very purplish-white character
that will remind you exactly of the color of the electronic flash on your camera (because it is the same technology).

The blue bulbs give headlamps a sick turquoise-blue-green coloring. Once
you have this information in mind, it is easy to spot a violator at half a mile.

If you have access to the vehicle in question and wish to make sure that the headlamp is being used properly, examine the lens and observe the markings. An arc-discharge headlamp MUST be labelled with one of the following codes:


If you see blue light from a headlamp marked HB1, HB2, HB3, HB4, HB5, or H1, H2, H3, H4, H7, or with no D-class or H-class marking at all, you have found a violator.

Daniel Stern
Automotive Lighting Specialist and Consultant
SAFE headlamp upgrades
Regulatory consultation

The views of the contributors to this publication are not necessarily the
position of On-Duty. They send it, you read it.

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