Vehicle lamps today are predominantly low voltage halogen lamps (12 Volt) specially developed for use in automobile headlamps or as supplementary interior vehicle lighting. The most common lamp type is the "H4", although the "H7" and corresponding headlamp systems are gaining ground. Xenon light, which is generated in gas discharge lamps for headlamps, is particularly bright. Lamps for supplementary lighting are used for reversing lights, brake lights, indicators, interior vehicle lighting, etc. LED systems play an increasingly important role in vehicle lighting; the first reversing and brake lights have already proved effective in practice. The lamp industry has also developed LED systems for day-time vehicle lighting.