Auto & Transport
Driving in heavy fog: what to do?
Heavy fog drastically reduces visibility and is a leading cause of multi-vehicle crashes. Learn how to adjust your driving and what to do if you get caught in it.
Written by Emily Brooks · Reviewed by Mark Robinson · Updated October 31, 2026 · 3 min read
Immediate actions
- 1 Slow down and increase your following distance.
- 2 Turn on your low-beam headlights and fog lights, never high beams.
- 3 Avoid sudden stops and use your turn signals early.
- 4 If visibility becomes too poor, pull off the road safely and turn on your hazard lights.
- 5 Stay focused and avoid distractions.
What not to do / warning
Heavy fog can cause multi-vehicle pileups. Slow down, use low beams, and never stop in the travel lane.
Driving in heavy fog is dangerous because it reduces visibility and depth perception, making it hard to see other vehicles, pedestrians, and road hazards. Fog can also create a false sense of security, leading drivers to maintain normal speeds. The following steps will help you stay safe if you encounter fog.
What to do first
- Slow down. Reduce your speed gradually and drive at a pace that allows you to stop within the distance you can see. Do not slam on the brakes.
- Turn on your low-beam headlights. Low beams are essential because they angle downward and illuminate the road without reflecting back into your eyes. If your vehicle has fog lights, use them. Never use high beams in fog; they reflect off the moisture and reduce visibility further.
- Increase your following distance. Leave more space between you and the vehicle ahead. A safe following distance in fog is at least 3-4 seconds, but in heavy fog, increase it further.
- Use your windshield wipers and defroster. Fog can cause condensation on your windshield. Keep it clear with wipers and your defroster.
- Avoid sudden stops. If you must slow down or stop, do so gradually and use your turn signals early to warn others. Tap your brakes gently to alert drivers behind you.
- Stay in your lane. Use the road markings and guardrails as guides. Do not drift into oncoming traffic.
- If visibility becomes too poor, pull off the road safely. Turn on your hazard lights, move as far off the road as possible, and stay in your vehicle with your seatbelt fastened. Do not get out of the car unless it is safe to do so.
What NOT to do
- Do not use high-beam headlights. They will reflect off the fog and make it harder to see.
- Do not tailgate. Rear-end collisions are common in fog.
- Do not stop in the travel lane. If you must stop, pull completely off the road.
- Do not rely on your vehicle's automatic headlights. They may not turn on in fog. Manually switch on your low beams.
- Do not use hazard lights while driving unless you are stopped or moving very slowly in an emergency. In some places, it is illegal to drive with hazard lights on.
When to seek help
If you are involved in a crash or your vehicle becomes disabled in fog, call local emergency services immediately. If you are stopped on the side of the road, stay in your vehicle with your seatbelt on and turn on your hazard lights. If you have to exit the vehicle, do so only when it is safe and move away from traffic.
How to prevent trouble
- Check the weather forecast before you travel and delay your trip if heavy fog is predicted.
- Ensure your headlights, fog lights, and taillights are working properly.
- Keep your windshield and mirrors clean inside and out.
- Familiarize yourself with your vehicle's fog light controls.
By following these steps, you can reduce the risks associated with driving in heavy fog. Always prioritize safety over speed.