High intensity headlights (HID) have many advantages over halogen headlights. They’re brighter, put less strain on the generator, and the higher color temperature makes it easier to see things like traffic signs at night. You may have even seen those blue or white headlights on older cars and wondered if it’s possible, or legal, to upgrade your car with aftermarket xenon bulbs.
Some of the cars you see on the road white or blue headlights, come with high intensity discharge (HID) light from the factory and they are completely legal. Other cars you see with blue headlights have questionable aftermarket modifications that can make it harder to see other drivers at night, and could even result in a ticket.
This is a rather complicated question when you get right down to it, but the simple answer is that you should check the specific laws you live under before putting in the car anything other than a standard spare lamps incandescent.
Stock halogen vs high intensity discharge
The reason why the issue of aftermarket headlights, often referred to as white or blue headlights, HID headlights, or xenon headlights, is so complex is that there are two kinds of aftermarket replacement headlights that can look blue and use completely different technologies.
Some «blue» headlights are regular blue-film halogen capsules, while others are actually a completely different type of lighting technology.
Most vehicles on the road today use either sealed-beam halogen headlights or capsule-type halogen headlights, where each headlight consists of a permanent reflector assembly and a halogen capsule. The first type requires replacing the entire lens and bulb together, while the other allows you to simply insert a new halogen capsule into a permanently installed reflector.
Factory HID lamps are similar to the second type, but instead of the reflector intended for the halogen capsule, they use projector assembly . This means that while you can buy HID capsules that will fit right into your factory headlight assembly, this can create problems with bright, out of focus beans that light up all over the place and therefore can cause problems for other drivers.
Where NHTSA stands for aftermarket HID headlights
Currently, most jurisdictions in the US require headlights to comply with Federal Motor Vehicle Safety Standards (FMVSS) 108, which states that headlight replacement capsules must match factory equipment dimensions and electrical specifications. This is a problem that HID headlights work differently than halogen headlights. For example, HID headlights use ballast, which is not required by halogen capsules.
NHTSA has a very narrow view of what is required to comply with FMVSS 108. According to the Washington State Patrol, for example, a HID replacement for an H1 halogen lamp must exactly match the size and location of the H1 lamp filament, electrical connector, and ballast, which is categorically impossible due to that H1 lamps don’t use ballasts in the first place.
In addition, the NHTSA found that HID conversion kits often exceeded factory headlight power ratings, often significantly. In some cases, measured aftermarket HID headlights have exceeded 800% maximum power halogen headlights, which they were supposed to replace.
Don’t trust dots
You may have heard that it is possible to install a HID conversion kit if it has the DOT logo on it, but the fact is that this mark only means that the company that made the product has self-certified it to comply with federal requirements. NHTSA, which is part of the US Department of Transportation, responsible for setting requirements , but does not actually certify that any product meets these requirements. So while there is such a thing as DOT compliance, there is no such thing as DOT approved headlight .
Since the NHTSA has officially stated that the HID conversion kit cannot comply with FMVSS 108, any DOT-approved mark on aftermarket HID lamps must be applied with salt added. As always, it’s important to find out what the product is and whether it’s actually legal, rather than just taking someone’s word for it.