Auxiliary Light Types

Auxiliary driving and fog lights are intended for use solely as auxiliary lighting. They are not intended to be used for headlight purposes, nor are they certified for headlight usage. Auxiliary lights are designed to improve visibility during night time driving and inclement weather.
Auxiliary driving lights are designed to provide relatively long range illumination forward of the vehicle that enhance the visibility of distant objects. Auxiliary driving lights are intended to be mounted above the vehicle's bumper or in its grill (in the case of off-road trucks, auxiliary driving lights are even mounted on the vehicle's roof or on top of its bed mounted roll bar). Auxiliary driving lights are intended to supplement the high-beam of a standard headlamp system. They are not intended for use alone or with the low-beam of a standard headlamp system.
Auxiliary driving lights are available in two types. The "standard" auxiliary driving light has a moderate beam width and is especially useful for higher speeds where they illuminate hazards and signs before they could be seen with the original high-beams only. The "pencil beam" driving light has an extremely narrow beam width and is especially useful for illuminating objects at the maximum distance. The "pencil beam" driving light is most often used for racing purposes
Auxiliary fog lights have a low, horizontal light cutoff to provide wide illumination over a relatively short distance ahead of the vehicle that enhances visibility in fog, rain, snow, or dust. An auxiliary fog light's relatively wide illumination can also be used to enhance visibility around tight bends and corners in clear weather. Auxiliary fog lights are intended to be mounted low (below the vehicle's bumper or in its grill) and are designed to be used in conjunction with standard headlight low-beams.
While auxiliary fog lights have traditionally been available with clear or amber lenses, the amber lens fog light is losing popularity because it has not proven to be more beneficial in foul weather than clear lens fog lights, is not as effective as a clear weather cornering light, and is often less geplementary to vehicle styling.
Irresponsible use of any auxiliary light can be dangerous and illegal. Lighting laws vary from state to state.