Everything you always wanted to know about vehicles but were afraid to ask
NCE the preserve of top-end models, socalled xenon headlights are becoming increasingly common on volume cars. Because they are brighter and illuminate a wider area than conventional headlights it has been argued that they improve road safety. The term xenon is, technically, incorrect.The lights are high-intensity discharge lamps (HID).They emit a bright, white light that is easily distinguishable from the yellowy halogen bulbs used on most cars. The term xenon became commonly used because xenon is added as a firestarter the other gases in the headlamp take time to react, so it is the xenon that provides the initial flash when the lights are turned on. The average HID lamp produces about 3,000 lumen from 42 watts of power while a halogen unit will give up to 2100 lumen from 65 watts.The stronger light means that xenon headlamps can be smaller — aesthetically more pleasing for most car designs — but are more expensive. One of the problems with HID lamps is that the difference between the illuminated areas of the beam and the darkness beyond is pronounced, while conventional headlamps offer a more natural shaded edge. The only way to convert from halogen to HID lighting is to replace the entire assembly, including the front glass, filters and lenses, with an HID unit.Aftermarket kits are of varying quality, however.They are expensive and require fitting and adjusting by a professional to avoid problems with badly aligned lights that dazzle oncoming drivers. Because HID lights contain a mix of gas and metals, broken xenon units are classified as special waste and must be disposed of correctly. Bi-xenon headlights use a single xenon lamp to produce both the main and dipped beam.The full light output is used for the main beam and a shutter blocks off part of the light when a dipped beam is required.