AC TMI White Paper: Actual Function of Automotive Fog Lights
Primary Function of Fog Lights
Automobile fog lights are typically designed to light up the road surface ahead of the car rather than the area farther down the road. The primary purpose of fog lights is to provide additional illumination in conditions of reduced visibility caused by fog, rain, snow, or mist. These conditions can cause light from the car's headlights to be scattered or reflected back, creating a glare that makes it difficult to see the road surface.
The purpose of fog lights is not to provide additional illumination at a greater distance down the road, as this can actually be counterproductive in foggy conditions. Light that is directed farther down the road can be reflected back by the fog, creating a glare that makes it even harder to see. Instead, fog lights are designed to provide a low, wide beam pattern that illuminates the road surface and makes it easier for the driver to see potential hazards in front of the car.
Mounting Fog Lights
To address this issue, fog lights are usually mounted low on the front of the car, below the headlights. They are aimed downward and slightly outward, illuminating the road surface and any obstacles that may be present, such as curbs or potholes. The beam pattern of fog lights is typically wider and flatter than that of headlights, providing a broader field of vision close to the ground.