When foggy weather sets in, driving can be difficult, especially when you turn your lights on. Regular headlights are aimed straight ahead, and most of the light will reflect off of the fog making it difficult to see. Fog lights are designed to improve visibility in these driving conditions, as well as during heavy snowfall, rain or any other time that it is difficult to see when driving.

Using regular headlights in foggy weather can make it even more difficult for drivers to see what lies ahead. In order to reduce the glare caused by fog, the special fog headlights are angled downward so the light bounces off of the low-hanging clouds and illuminates the road in front of you. They also make it easier for other drivers to see you coming when visibility is reduced due to fog, snow or heavy rain.

There are three main types of fog lights, halogen, light-emitting diode (LED) and high-intensity discharge (HID) bulbs. Halogen bulbs are the most commonly used lights for fog lamps, and many manufacturers use coated lenses to increase visibility that gives them an amber hue. Both LEDs and HIDs tend to be brighter and more effective than standard halogen bulbs, but there are a few differences.

LED bulbs use very little power, and they are less prone to breaking or burning out than ordinary bulbs because they do not contain filaments to generate light. The diodes come in a variety of colors, but for the most part these are merely a stylist choice and do not alter the effectiveness of the lights. Many automakers have begun to include LEDs on the headlights of their vehicles, since they first emerged in the automotive market in 2004 on the Audi A8. The German car company now uses these bulbs for the daytime running lights on most of its newer models.

HID bulbs, which emit a white-blue light, use electricity to charge the xenon gas contained within, so they are like LEDs in that there is no filament to break. The first HID bulb was used in a BMW 7 Series car in 1991, and since then many car companies have adopted the use of the light, but it is rarely a standard option. These lights typically last about 2,000 hours before they need to be replaced, which is about twice the lifespan of a halogen bulb.