Headlights

Headlights are vehicle lighting devices that illuminate the road ahead and signal presence to other road users. They are designed to provide visibility in low-light conditions, improve detection of pedestrians and obstacles, and help other drivers gauge distance and speed. Headlights typically produce two beam patterns: a low beam (also called dipped or pass beam) for regular night driving and oncoming traffic, and a high beam (or main beam) for extended range when traffic is clear.

Historically, headlamps evolved from acetylene and oil lamps to electric incandescent lamps, with sealed-beam units widely adopted in the mid-20th century. Modern headlamps rely on halogen, high-intensity discharge (HID) xenon, and light-emitting diode (LED) technologies. Some systems use projector lenses or reflectors to shape beams, and many vehicles employ adaptive or matrix headlights that adjust intensity and direction to improve illumination while reducing glare.

Regulatory standards govern headlight color, intensity, and alignment. In North America, the United States and Canada commonly follow DOT/SAE specifications; in Europe and many other regions, ECE regulations apply. In most jurisdictions, headlights must be aimed correctly and replaced when diminished. Daytime running lights are required or optional in some regions to increase daytime visibility. LED and adaptive systems typically offer greater efficiency and faster response than traditional halogen lamps.

Maintenance and design considerations include keeping lenses clean, ensuring proper aim, and replacing bulbs as needed. Effective headlights balance visibility and glare control, supporting safer driving in varied weather and lighting conditions.