Quote Originally Posted by sensei_ View Post
dirt distort light. on high speed highways and country road headlights are easily soiled, hence washers. afterall if you are travelling long distance and high speed its nice to be able to see up in front of you.

pretty sure for HIDs they are also a legal requirement.
I know the bit that they clean the lights... like volvo had them a long time ago. But why apply these to HID only and not to regular lights? The ADR rules make me confused half the time. :-/