What is the function of a car's fog lights?

[MacHarmony]

The fog lights of a car serve to alert vehicles in front and behind and prevent accidents. In weather conditions with low visibility, they allow vehicles or pedestrians to notice the car early to prevent accidents. Situations for using fog lights: 1. Heavy rain where the driver's visibility is blurred, making it difficult to judge the surroundings; 2. Foggy weather; 3. When driving at night with no streetlights or poor lighting; 4. Encountering low visibility conditions such as fog, rain, snow, dust, or hail. The fog lights are located on the left rear or left side of the steering wheel. Types of fog lights: 1. Button-operated fog lights; 2. Turn signal lever knob-type fog lights; 3. Center console knob-type fog lights.

[DiCaden]

I often drive on mountain roads, and fog lights are literally lifesavers. Regular headlights create a glaring white wall of light in foggy conditions, making it hard to see far ahead. But fog lights are different—they're positioned low and project light horizontally, offering superior penetration. The design often uses yellow or white light for a reason: yellow light has a longer wavelength, scattering less when it hits fog particles, thus providing better visibility. I've been in situations with heavy fog where visibility was less than 10 meters, and fog lights allowed me to barely make out the roadside markings. More importantly, they help oncoming drivers spot you earlier. But a word of caution: never use them in clear weather—their brightness and angle can blind drivers behind you.

[VanWilliam]

Speaking of the pair of red lights at the rear, many people think they are just decorative. In fact, the red fog lights have three times the warning effect of brake lights in rainy or foggy conditions. The principle is simple: red light has a longer wavelength, making it much more visible than yellow in poor visibility. When encountering dense fog on the highway, I immediately turn on both front and rear fog lights. Cars behind can spot the two red glows from hundreds of meters away, buying me precious seconds to react. If you’ve seen accident footage, you’d know that a car without fog lights in heavy fog is practically invisible—by the time the trailing vehicle sees the taillights, it’s often too late to brake.

[SanKimberly]

The greatest value of fog lights is to improve the driver's visibility. When driving on the highway in the rain, the water film on the windshield refracts oncoming headlights into a halo. At this point, turning on the front fog lights, which cast light close to the road surface, can clearly outline the edges of the lane markings. Once during a typhoon while crossing a sea bridge, crosswinds blew rain horizontally, rendering the headlights completely ineffective. It was only by relying on the fog lights illuminating the right shoulder that I could inch forward slowly. However, it's important to note that many vehicles require the headlights to be turned on before the fog lights can be activated, a design intended to prevent accidentally blinding others.

[VonJaxon]

That winter in Changbai Mountain, the visibility was less than five meters in the blizzard. The convoy moved forward cautiously with hazard lights on, only to find that vehicles with yellow front fog lights were easier to follow. The fog lights created two low-angle beams in the snow, guiding the way like railroad tracks. Later, the mechanic explained that fog lights are deliberately installed below the bumper to avoid direct glare from snowflakes. So, turning on fog lights in rain or snow isn’t for illuminating the road, but for being seen and finding reference points.

[DelIsabelle]

Many people think the brighter the fog lights, the better, but in fact, regulations have strict requirements on brightness and angle. Front fog lights must be positioned lower than the headlights, with an upward angle limit of 15 degrees to prevent direct glare into the eyes of oncoming drivers. Rear fog lights are even more strictly regulated—European standards require them to illuminate on only one side to avoid confusion with brake lights. Once, while driving a friend's American-spec car, I noticed its rear fog light was half as bright as those on European-spec cars, which made me realize how much standards vary by region. Remember, fog lights are special tools, and misuse can be dangerous.