When headlight beams were circular, the driver's side beams had to be aimed lower to prevent shining into oncoming drivers eyes. This is no longer the case on modern vehicles.
When I replaced my coke bottle bottom North American sealed beam headlights (the laws back in the '50s stated that headlights had to be sealed beam so that they didn't rust) back on my old 1971 Volvo with a pair of Bosch H4 Halogen, the package came with aiming instructions. I don't remember the details, but I do remember that both beams were aimed exactly the same - straight ahead and at the same height above the ground so many feet from the car on a level surface. You could do this because of the shadow pattern of the low beam, which prevents the light from shining into oncoming drivers eyes.
The modern halogen and HID headlights on BMWs have the same pattern. There's absolutly no reason to aim the driver's side light lower than the passenger's side, unless there's still some regional law still on the books which requires it.
I aim mine by going to a deserted, level stretch of road on a dark night. The low beam has a shadow with runs horizontally from the left to the center of the beam, after which it angles up at about 45 degrees. This shadow is what protects the oncoming drivers. By lining the car up on the dashed center divider line, one light at at time, I can make sure that both beams are pointing straight down the road by turning the horizontal adjusters. Then I turn the vertical adjusters so that the horizontal shadows on low beams hit the pavement just about at the limits of vision. If you can see the shadow on the pavement, you know that you're not shining light into oncoming driver's eyes. There you have it. Straight and allowing you to use all of the visible low beam that you can.
I've done this for more than 30 years now and I know that my lights don't bother oncoming traffic because there have been several times that I've met my own car when my wife was driving it.
The halogen H4 bulbs (not used often anymore, mostly H2's now) have two filaments in them. The low beam filament has a cup around it which causes the shadow that you see. HID lights are different. They only have one arc (rather than a filament) and a mechanism moves into place when on low beam which blocks some of the light to protect oncoming drivers. If you want to see it work, point your lights at a building and flip back and forth from high to low. You'll notice that the lower half and right side of the beam don't change, but a shadow drops down into the upper left portion of the beam.
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