Headlights

http://en.wikipedia.org/wiki/Headlamp

More info above.

Retrofitment
When a halogen headlamp is retrofitted with an HID bulb, light distribution and output are altered.[32]In the United States, vehicle lighting that do not conform to FMVSS 108 are not street legal.[32] Glare will be produced and the headlamp's type approval or certification becomes invalid with the altered light distribution, so the headlamp is no longer street-legal in some locales.[33] In the US, suppliers, importers and vendors that offer non-compliant kits are subject to civil fines. By October 2004, the NHTSA had investigated 24 suppliers and all resulted in termination of sale or recalls.[34]
In Europe and the many non-European countries applying ECE Regulations, even HID headlamps designed as such must be equipped with lens cleaning and automatic self-leveling systems, except on motorcycles. [33] These systems are usually absent on vehicles not originally equipped with HID lamps.
 
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