What is the brightest hid headlight allowed by law?

Answer 1

There are about twelve different legitimate HID bulb types: D1R, D1S, D2R, D2S, D3R, D3S, D4R, D4S, D5R, D5S, 9500 and a few others. They all produce about the same amount of light (around 3,000 lumens), and they all produce light of about the same color temperature (4100K to 5000K); any nonstandard color temperature or lumen output is illegal. The differences among the various bulb types are physical and/or electrical to work with different kinds of headlamps and different kinds of electrical control gear. The end user does not get to choose which type of bulb to use; that decision is made at the headlamp design stage—each headlamp accepts only one kind of bulb, and putting in the wrong kind ruins the safety performance of the headlamp. Headlamps originally designed, built, tested, and certified as HID headlamps are legal in all 50 states. There is no such thing as a (legitimate) HID bulb to fit in place of a halogen bulb ("H1 HID bulb", "H4 HID bulb", etc.). So-called "HID kits" to convert halogen headlamps are widely available, but they are (all) illegal and dangerous; halogen headlamps must use halogen bulbs.

As for the headlamps themselves: their performance is specified in US and international regulations as a series of "test points" within the beam pattern. At each test point, there is an allowable range of intensity. Within the requirements in the regulations, each automaker and each headlamp maker has its own internal standards for what they consider to be a good headlamp. It isn't possible to identify "the brightest headlight".