[davepl]

As a bit of trivia, HID systems were not allowed on production cars in the US until and unless the manufacturer system included auto-leveling. They're bright and you don't want them in the eyes of other traffic.

On the European cars there could be a dial on the dash. But I guess they were afraid we Americans would put 20 cases of Budweiser in the trunk and drive around with our headlights blinding other drivers.

Now that I think about the conduct of the average driver, though, they might be right! It's rare enough for people to properly signal turns around here let alone adjust their headlights to compensate for vehicle loading.

Want more?

There's a height limit on how high you can put them, so if you look at large vehicles like the Rolls Royce Phantom or certain SUVs you'll see that the HID headlight itself is actually low, like a driving light, and what looks like conventional headlights are pretty much decorative.