They don't work. All the time I see what looks like flashing as the "clever" automatic headlight tries to work out if I'm there or not. Countless times I've had someone driving behind and hogging the lane to the right of mine and have their full beams shining through my mirrors. Moving into the same lane in front of them causes their headlights to dip, but I shouldn't have to do this (especially because being in that lane is against the highway code).