Xenon lamps on cars

Question

I have noticed that HID (xenon) lamps are being sold as aftermarket accessories for cars that do not have them as original equipment. Is this legal? My understanding is that cars that come out with factory fitted xenon lamps also have automatic levelling mechanisms to avoid blinding oncoming drivers. The aftermarket kits do not have this feature.

Answer

The issue is quite interesting - Regulations 159 (Head Lamps) through to 161 (Dipped Beam) deal specifically with the "main lights" for driving. I have specifically ignored all other types of lamps (as these are generally not involved in the xenon after-market replacements). The legislation does not refer to anything in terms of the TYPE of bulb but does refer to adjustment of the light illumination area and direction. This would need to be done MANUALLY at a test centre or facility capable of measuring the required angles, etc for the lights. Legislation does, however, refer to the COLOUR of light emitted and, it would be interesting to discuss the colour of these xenon bulbs as they do appear BLUE which is illegal (Regulation 176: Identification Lamps, paragraph (3) (a)).