Rick's Free Auto Repair Advice

LED headlight bulbs legal?

Are retrofit LED headlight bulbs legal?

Retrofitting LED bulbs into a headlight designed for halogen bulbs is NOT legal. First, the Department of Transportation sets the standards for headlight bulbs. If the carmaker designed the headlight to accept halogen bulbs, that’s the only bulb you can legally install. That’s because the location of the filament and the reflector design is matched to provide the proper beam pattern. You can’t change just one component and get the same beam pattern, no matter how much it’s re-aimed.  So a factory-installed projector headlight assembly that’s been DOT certified to accept a DOT certified  H11 halogen capsule bulb cannot, under any circumstances legally be fitted with either an H11 compatible HID or LED bulb. Period.

In summary, It’s illegal to retrofit LED headlight bulbs into a headlight assembly designed for halogen bulbs.

Second, tests conducted by the Society of Automotive Engineers (SAE) show that LED bulbs actually throw LESS light on the road, despite the fact that the LED manufacturers advertise higher lumen output levels than halogen bulbs. For details on the SAE technical paper, see this post.

LED bulbs don’t carry a DOT certification

I’m not aware of any brand of LED bulb that carries a DOT certification even though some bulbs claim they “meet current regulations,” which is ironic since there is no way an LED bulb can meet current regulations without the DOT certification.

To get around this illegality, some LED bulbs state they’re approved for “off-road use only.” That should be your warning that you can’t install them for use on normal roads.

Read the D.O.T letter at the end of this story and read about the legal liability issue here. The lawsuit mentioned is about tail-lights, but the liability issue is the same: If you change the lighting from the factory and it causes an accident you are liable.

Many LED bulbs don’t fit into factory headlight assemblies

Most LED bulbs have a fairly large heat sink on the connector side of the bulb. The heat sink assembly often interferes with the fit under the hood and often prevent the reinstallation of the factory headlight cover.

But they sell LED headlight bulbs everywhere

Hey, it is not illegal to manufacture and sell retrofit LED bulbs it’s just illegal to install them in a headlight assembly designed for halogen bulbs. Look anywhere in auto parts stores or online and you’ll find a huge assortment of retrofit LED headlight bulbs. They don’t require any wiring modifications, most fit into your existing headlight assemblies (although due to the heat sink arrangement, many don’t fit well under your hood), and they tout much higher lumen output. Sounds too good to be true, right. Well, it is.

Will LED bulbs cast more light ON THE ROAD

No. Here’s where the irony comes into play.

LED headlight bulb

Multiple diodes=Multiple focal points=light scatter and glare

LED bulbs claim they output produce more lumens than a standard halogen bulb. Even if that were true (and SAE actual tests show that the majority of the LED bulbs don’t come close to their advertised lumen output–in some cases by 70% less) the actual light cast on the road is dependent on the placement of the focal point of the reflector and bulb. See this post for the results of the SAE LED headlight study.

LED bulbs in a reflector headlight assembly designed for halogen bulbs

A reflector headlight must be designed for a single focal length bulb with an exact filament size and locations. However, LED bulbs generate light from multiple circuit-on-board (COB) chips placed in various places on the bulb frame, so the light sources are NEVER in the same place as a filament bulb. That means they can never work the same in a reflector or projector headlight designed for a single filament.

Led headlights

Notice the multiple LEDs and the location of the LEDs. They don’t match the location or size of a halogen filament

In other words, an LED bulb with multiple hot spots installed in a headlight designed for a halogen filament bulb will not cast the light properly. Neither a reflector headlight nor a projector headlight can compensate for light scatter coming off the reflector from an LED bulb with multiple light sources.

Simply put, it can’t properly focus light that comes into the lens from the wrong angles. So since the LED light source located closest to the halogen focal point is the light that will be concentrated by the projector lens. In other words, if you install retrofit LED bulbs in your old halogen headlight assembly, you’ll cast LESS light on the road and cause more glare into oncoming vehicles.

headlight replacement cost

This image shows a halogen bulb in a halogen headlight assembly. Notice how the parabolic reflector focuses the light into a direction straight-ahead pattern.

HID conversion kit

This image shows what happens if the focal point is closer to the reflector. See how the light scatters up and down, with almost no light being cast straight out.

In this image, you see what happens if the light source is moved away from the reflector. The result is more light shining into oncoming traffic and the trees, and down towards the road—but not forward.

It’s illegal even if you have a projector headlight

Even if you have projector headlights, you still can’t use a different bulb. Here’s why. A projector headlight still has a reflector, but that reflector focuses the light to a midway point between the reflector and the lens. The lens then refocuses the light for maximum output on the road. Once again, the reflector used in a projector headlight is designed for whatever bulb was installed at the factory. Change the bulb and you change everything.

projector headlight with halogen bulb

Projector headlight with halogen bulb. The reflector focuses the light midway and the lens refocuses it.

projector headlight with led bulb

Change the bulb and the beam no longer focuses midway between the reflector and the lens. So less light gets refocused on the road and since the focus is off, more light ends up as glare.

When you get caught by the law

Why do I mention the law? Because cops stop you because of the glare. THAT’s how you get caught by the police. The glare gives you away.

LED headlight bulbs expose you to legal liability

The glare you throw into oncoming traffic can cause accidents. If your LED retrofit bulbs cause glare and that glare causes an accident, YOU can be sued for not driving with illegal and non-compliant headlights. Oregon State Police Senior Trooper Douglas Brown states, “I’ve had cases where they’ve swerved across into the oncoming lanes and hit the car that was blinding them.”

LED headlight bulbs are notoriously unreliable

LED bulbs have large cooling fins that extend outside the headlight assembly. Some LED bulbs have fans to help cool the electronics. They’re far more expensive to buy and they tend to fail faster than standard halogen bulbs. The estimated life (in hours) never quite matches the actual life once in the vehicle. Put it all together; less light on the road, more glare for oncoming traffic, higher cost, and shorter life and it just doesn’t make sense to convert to LED headlight bulbs.

For the doubting Thomases

Here’s a legal interpretation of the law from the legal counsel of the National Highway Traffic and Safety Administration:

Here’s the link if you want to verify this

Mr. Simon S. Shih

4 Teal

Irvine, CA, 92604

Dear Mr. Shih:

This responds to your e-mail, in which you seek clarification regarding the legality of high intensity discharge (HID) headlamp conversion sets, specifically whether it is legal to manufacture or sell sets of HID headlamps to replace original equipment halogen headlamp sets. We are pleased to have the opportunity to answer your questions related to Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices and Associated Equipment.

By way of background, the National Highway Traffic Safety Administration (NHTSA) is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment. As a preliminary matter, we would clarify that we have no authority either to approve or disapprove motor vehicles or items of motor vehicle equipment. We do advise correspondents of the relationship of their products to applicable FMVSSs and other regulations that we administer. If a product is covered by one or more of our safety standards, its manufacturer must certify compliance of the product with all applicable FMVSSs prior to its importation or offering such product for sale. The symbol “DOT” on replacement lighting equipment is often mistaken for “DOT approval” of the equipment, but, in fact, it reflects the manufacturer’s own certification of compliance.

We believe that your questions are addressed by our March 13, 2003, letter of interpretation to Mr. Galen Chen (see enclosure). In that letter, we interpreted FMVSS No. 108 as requiring headlamps manufactured to replace original equipment headlamps to comply with all applicable photometry requirements using the replaceable light sources intended for use in the headlighting system on the vehicle for which the replacement headlamp is intended. Unlike other lamps, FMVSS No. 108 specifically regulates headlighting systems, including their light sources (see S7.1, S7.5, and S7.7). We adhered to this interpretation in a recent interpretation to Calcoast-ITL (69 FR 60464 (Oct. 8, 2004))(see enclosure).

Because replaceable light sources are, by regulation, designed to be non-interchangeable, it would not be possible for an HID headlamp conversion set to meet the standard’s photometry requirements for an original equipment headlamp system using a halogen light source, so the replacement lamps could not be sold for this purpose. Furthermore, a headlamp dealer or motor vehicle repair business could not remove the original halogen headlamps and install HID replacement headlamps without violating 49 U.S.C. 30122. That section prohibits manufacturers, distributors, dealers, and motor vehicle repair businesses from making inoperative equipment installed in accordance with a Federal motor vehicle safety standard. We cannot comment on the specific replacement lighting products that you mentioned because we do not have sufficient information on them.

Finally, in a subsequent e-mail, you asked whether our regulations require HID lighting systems to include “auto-leveling” and washing systems, similar to those incorporated in vehicles sold in Europe. The answer is no. FMVSS No. 108 does specify aimability performance requirements under paragraph S7.8 of the standard, but that paragraph does not require an “auto-leveling” capability. The standard also does not contain any requirement for a headlamp washing system.

It may be of interest to you, we also have enclosed a copy of our November 18, 2002, letter of interpretation to Mr. Jeff Deetz, which relates to kits that substitute the type of light source in existing headlamps.

I hope you find this information useful. If you have further questions, please feel free to contact Eric Stas of my staff at this address or by telephone at (202) 366-2992.


Jacqueline Glassman

Chief Counsel





© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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