Bi-xenon headlights, or high-intensity discharge (HID) headlights, are low- and high-beam forward-facing car lights that use electronically controlled gas-discharge lamps to illuminate the road ahead. They emit a distinct bluish light.
Xenon headlights create an electrical arc between two electrodes that excites the xenon gas. The gas vaporises metallic salts that sustain the arc and emit the light. These lights have a mechanical plate that shields part of the light; this retracts when the driver switches to high beams.
Bi-xenon lights are popular with some car manufacturers because they emit a brighter and more consistent light than traditional halogen headlights, making it easier for drivers to see. Xenon headlights also use two-thirds less power than traditional headlights and last two to three times longer.
Many manufacturers don't offer bi-xenon headlights as standard equipment, making them costly to add to your vehicle. These lights can also experience mechanical failures due to the design of the mechanical shutter. This is not a problem with sealed-beam, composite lights or even standard xenon lights. Bi-xenon headlights can cause significant glare for other road users, impairing the vision of oncoming drivers or pedestrians.