Dear Tom and Ray:

I need your help with an issue that's come up between my girlfriend and me. She recently installed halogen headlights on her car. And I hate halogen headlights. HATE them. I am very prone to migraines, and I find that having halogen headlights coming at me triggers migraines something awful. She says that staring into any headlight will make your head hurt. I say they're really inconsiderate of other drivers. She says they're cool. I should add that we live in Sydney, Australia, and the roads are busy and well-lit, and her vision is fine. What do you think? And do you have any suggestions on how to use halogen headlights safely and considerately (if that's possible)? -- Elena

TOM: Elena, I'm going to guess that you don't drive toward your girlfriend that often. And that your concern is less about her giving you migraines than it is about her being a good citizen.

RAY: I'm also going to guess that you really mean to impugn xenon or HID (high-intensity discharge) headlights, not halogens. Halogens have been in common use for 30 years now, and almost all cars have them. We know there's a lot of ocean between here and Sydney, Australia, but I trust that the halogen bulb got there several decades ago, along with other cultural staples like the microwave oven and Bermuda shorts.

TOM: Xenon headlights, however, can be a bit distracting. They have a blue hue to them, and they are brighter than standard halogen bulbs. But they also offer excellent visibility at night -- at least for the driver who has them!

RAY: And, like death, taxes and the Red Sox losing in September, they're more or less inevitable now, as people discover their superior lighting and aiming capabilities.

TOM: So, let's concentrate on how to use them safely and considerately. First of all, you say your girlfriend just got them, which suggests to me that she might have bought "aftermarket" HID bulbs from an auto-parts store. Some of these are not xenon bulbs at all. They're cheap knockoffs that are simply excessively bright lights with a blue tinge. They're just designed to look like xenon bulbs, which some people find cool.

RAY: These fakes, in and of themselves, can be obnoxious (and oftentimes illegal) because, unlike real xenon headlights, their light beams can't be focused precisely. So you just get a very bright blue light, shining in all directions from an oncoming car. And that IS dangerous to other drivers.

TOM: Even if she got real aftermarket xenon bulbs (which cost hundreds of dollars -- if she bought hers for $79.95, they're not the real thing), they might not be aimed correctly. One of the great advantages of xenon bulbs is that they have a very precise light beam, which can be cut off at a certain height to prevent the blinding of oncoming drivers. But if they're aimed too high, they can be very distracting.

RAY: So, if your aim is for your girlfriend to be considerate, you'll want to check first to see if she got real xenon bulbs. If not, she should really consider yanking them out. If her headlights are real, have her take the car to a shop and make sure they're aimed correctly.

TOM: By the way, some new cars with xenons (Infiniti comes to mind) even have a bulb-height-adjustment switch on the dashboard now. So, when you have three mothers-in-law in the back seat and the front of the car is pointing toward the constellation Orion, you can aim the headlights lower and avoid blinding oncoming drivers. Now that's considerate!