[-kj-]

It has to do with the light beam cutoff pattern, (the point at which the light shines directly into oncomming traffic).

Factory HID systems are usually in projector housings, which put the beam into a highly focused, narrow pattern... equivilant to halogen reflector housing... but more intense. All while NOT blinding oncomming drivers.

Halogen systems have a sharp beam pattern cutoff without the projector lense due to the bulbs light emiting properties.

Once you add the HID bulb to a factory halogen reflector (which are 99% of "plug&play" systems), you get a widely scattered beam that blinds the crap out of other drivers and dosen't do as well of a job at lighting up the road. Effectively sacraficing all of the befifits of HID just for the "cool look of HID".


I'd imagine if you got some DOT projector beams and installed the HID bulbs you would be perfectly legal.