Best Practices and Legal Requirements for Using Fog Lights When Driving in Fog？BLIAUTO Professional Lighting Safety & Regulation Guide

Driving in foggy weather is a challenge for every driver. Heavy fog significantly limits visibility and greatly increases the risk of traffic accidents. In such conditions, proper use of fog lights not only helps drivers better observe the road but also plays a critical role in ensuring driving safety and complying with legal regulations.

As a brand specializing in automotive lighting solutions, BLIAUTO will guide you through the best practices for using fog lights in foggy conditions and explain the key regulations to be aware of—based on real-world driving experience and both domestic and international standards.

1. Basic Function and Purpose of Fog Lights

Fog lights are divided into front and rear types, each serving distinct purposes:

Front fog lights: Mounted low on the front bumper, these emit a wide, diffused beam with strong penetration power to illuminate close-range road surfaces, helping the driver identify road edges, signs, and obstacles in low-visibility environments.

Rear fog lights: Mounted at the rear of the vehicle, they emit a strong red light to alert vehicles behind of your presence, reducing the risk of rear-end collisions.

Fog light beam colors are typically yellow or white (front fog lights) and red (rear fog lights), offering strong penetration and high visibility.

2. Best Practices for Using Fog Lights in Foggy Conditions

1. When to Turn on Fog Lights

Fog lights are not always necessary. They should only be turned on under the following conditions:

Visibility is below 200 meters (such as during heavy fog, smog, rainstorms, or sandstorms);

Headlights fail to adequately illuminate the road ahead due to extreme low light;

Wet or reflective road surfaces cause glare, where fog lights help reduce reflection.

Using fog lights in clear weather can cause glare to other drivers and may lead to penalties under traffic laws.

2. Avoid Using Fog Lights with High Beams

In foggy weather, high beams tend to reflect off the fog, creating a "white wall" effect that reduces visibility. It’s recommended to use a low beam + fog light combination for optimal visibility without affecting others.

3. Use Tail Lights and Hazard Lights Together

Ensure that your tail lights, brake lights, and rear fog lights are working properly. In extreme conditions, turning on hazard lights (double flash) can help alert nearby vehicles to maintain safe distance, especially on highways or when driving slowly.

4. Adjust Speed and Following Distance

Fog lights are not a substitute for safe driving behavior. In low-visibility situations, always reduce speed and increase following distance:

On highways: maintain at least 100 meters of distance;

In urban areas: keep a gap of at least two vehicle lengths when driving at low speed.

3. Fog Light Regulation Summary in China

According to GB 4785-2019 ("Installation regulations for external lighting and signaling devices of automobiles and trailers") and relevant traffic laws:

✅ Legal Requirements:

Front fog lights are optional but must be symmetrically installed, and mounted no less than 250mm from the ground;

Rear fog lights are mandatory safety features, and at least one red rear fog light must be installed;

Rear fog lights may only be used in low visibility conditions and must be off in normal weather;

Beam color must comply: white/yellow (front), red (rear);

Brightness and beam shape must ensure strong penetration without causing glare.

❌ Common Violations:

Not using fog lights during foggy conditions, creating safety hazards;

Using fog lights in clear weather, blinding other drivers;

Installing non-compliant aftermarket fog lights (e.g., multi-color or strobe lights);

Overpowered fog lights or improper lenses leading to glare and disturbance.

4. Fog Light Regulations in Europe & the US

For international users or cross-border drivers, here’s a brief overview of foreign regulations:

Europe (ECE R19): Front fog lights may emit white or yellow light and must have E-Mark certification; rear fog lights must be bright and symmetrically positioned.

USA (FMVSS 108): Front and rear fog lights are optional; rear fog lights must be independently controlled to prevent accidental activation.

5. Frequently Asked Questions (FAQ)

Q1: What’s the difference between fog lights and headlights?

A: Fog lights provide wide, short-range, scattered light with strong penetration, ideal for foggy weather. Headlights (low/high beams) offer focused, long-range lighting that may cause reflections in fog.

Q2: Can I use fog lights on clear nights or sunny days?

A: No. Fog lights are too bright for normal conditions and can blind other drivers. Misuse may result in fines or point deductions.

Q3: Can fog lights replace headlights?

A: No. Fog lights are for supplementary lighting in low visibility. They do not provide sufficient distance illumination or meet legal headlight requirements.

Q4: Do all cars come with fog lights?

A: Not all. Front fog lights are often optional or come with mid-to-high trims, while rear fog lights are mandatory on all vehicles sold in China.

Q5: Can I install fog lights by myself?

A: Yes, but only if you have electrical knowledge. It’s best to have them installed by a professional to ensure proper wiring, sealing, and beam adjustment.

Conclusion: Fog Lights Are a Lifeline, Not a Decoration

From the moment you turn on your fog lights in poor visibility, you’re taking a vital step toward safer driving. Proper and legal use of fog lights is not only a responsible driving habit—it’s a requirement under the law.

As a brand committed to vehicle lighting safety, BLIAUTO continues to provide high-performance, reliable fog light products and expert usage guides to help you drive with confidence—even in the worst weather.