headlight

Headlights are front-mounted lighting devices on motor vehicles that illuminate the road ahead and make the vehicle more visible to other road users. They operate in low-light conditions, at night, and in adverse weather, contributing to driving safety and situational awareness.

Headlight assemblies typically contain a light source, optics to shape the beam, and a housing with seals to protect against moisture. Common sources include halogen bulbs, high-intensity discharge (HID) lamps, and light-emitting diodes (LEDs). The optics determine the beam pattern to balance road illumination with glare limitations for oncoming drivers.

Beam patterns include a low-beam (dipped) pattern to illuminate the road ahead without dazzling others and a high-beam (main) pattern for maximum visibility on unlit roads. Many modern systems incorporate adaptive or automatic features that adjust the beam in response to traffic, weather, and road conditions.

Regulatory standards govern headlight performance, color, mounting height, and electrical systems. Regions typically have separate standards such as European ECE and United States SAE/JIS, with differences in beam patterns and testing procedures. Lenses must be kept clear of dirt and oxidation to maintain light output and reduce glare.

Maintenance and alignment are important for safe operation. Bulbs wear out and lenses can degrade, reducing brightness or causing glare. Regular cleaning, proper aim, and using the correct bulb types help ensure consistent performance. History-wise, headlights evolved from acetylene and oil lamps to electric systems, with sealed-beam, halogen, HID, and LED technologies marking successive improvements in efficiency and reliability.