Driving in Fog: CARIFY’s Tips for Safe Driving

Ever experienced this? You're driving on the highway in fog and suddenly can barely see the lights of the vehicle in front of you, let alone the lane markings. Driving in fog poses unique challenges for drivers. Especially in autumn, you must be prepared for fog and drastically reduced visibility at any time. In Switzerland, this is particularly noticeable when driving through the lowlands, where fog banks often settle in valleys.

Poor visibility and slippery roads are a dangerous combination. Accident statistics from the Federal Roads Office (Astra) from 2020 to 2024 show a clear increase in road accidents starting in September. Most accidents occur in November and December.

Given this, it’s crucial to understand the necessary safety measures and how to behave when driving in fog. At CARIFY, we’ve gathered key tips to help you navigate foggy roads safely.

Important Information About Fog Conditions

How does fog form? When temperatures drop, moisture in the air condenses into tiny water droplets suspended in the air. Several weather conditions must coincide for fog to form:

• High humidity: When relative humidity reaches or nears 100%, the air is saturated with moisture.

• Temperature drop: Cooling air causes water vapor to condense into droplets.

• Calm winds: Under high-pressure conditions, there's little wind at lower altitudes to disperse the fog.

• Clear skies: Without clouds, heat escapes the ground more quickly, cooling the surface.

In mountainous regions, fog accumulates in valleys and depressions, but it can also form at higher altitudes. These tiny droplets affect visibility in several ways:

• Light scattering: Light beams hitting water droplets scatter, making light sources appear blurry and dim.

• Visibility: The denser the fog, the shorter the visibility—sometimes just a few meters, making it harder to react to obstacles.

• Depth perception: Fog distorts distance perception, making objects appear closer or farther than they really are—this makes driving even more dangerous.

Fog mostly occurs at night when temperatures are lowest, adding darkness to the already reduced visibility. It also creates a film of moisture on asphalt, decreasing tire grip. When temperatures fall below zero, this can lead to black ice and increased slipperiness.

The Importance of Reducing Speed

Slippery roads and poor visibility significantly raise the risk of accidents in fog. Other road users can suddenly appear out of nowhere—and you must be able to stop in time. Keep these points in mind:

• Delayed reaction: Distance is harder to judge, and obstacles are perceived later, delaying your response time.

• Reduced concentration: Fog strains your eyes and causes fatigue more quickly.

• Longer braking distance: Wet or icy roads increase stopping distances.

So, always adjust your speed to ensure you can stop safely. The legal speed limit is usually too fast under foggy conditions.

Rule of thumb: Visibility in meters = your speed in km/h.
Tip: Use the roadside reflectors spaced every 50 meters to estimate visibility. If you can only see one, visibility is under 50 meters. In that case, do not exceed 50 km/h.

Safe Following Distance in Fog

You're driving on the highway in fog and just saw the taillights of the car in front disappear into the mist. Don't speed up to follow those lights!

1. The driver in front can’t see much either.

2. You're driving too close.

3. Your proximity might pressure them to speed up unnecessarily.

Because of longer braking distances in fog, you must maintain a safe distance to react in time if the car in front brakes or an obstacle appears.

Rule of thumb: Minimum distance = your current speed in meters.

Using Fog Lights

Being able to see and be seen is crucial in fog. But don’t use your high beams! Thankfully, vehicles come equipped with fog lights made specifically for poor visibility.

In Switzerland, fog lights follow these rules:

Rear fog light:

• Symbol: Red icon with a half-circle and three lines pointing right, crossed by a squiggly line.

• Advantages: The bright rear fog light is more visible and scatters less than standard brake lights.

• Rules: Use it only when visibility drops below 50 meters. Use is optional, not mandatory.

• Tip: The bright light may distract drivers behind you. Turn it off once you know you’ve been seen.

Front fog lights:

• Symbol: Green icon with a half-circle and three lines pointing left, crossed by a squiggly line.

• Advantages: These are mounted lower, illuminating the road better with less reflection. Their broad, yellowish beam is less scattered by fog.

• Rules: Only use them when visibility is under 50 meters.

• Tip: Using fog lights with low beams may dazzle others. In thick fog, switch to parking lights + fog lights.

Note: In Switzerland, unlike in Germany, you’re not required to use fog lights. Use of fog lights and rear fog lights is only permitted in very low visibility.

Practical Tips for Driving in Fog

Your safety matters. Here are more essential tips for staying safe in fog:

• Expect icy roads: Fog droplets can freeze quickly on cold surfaces, creating black ice. Avoid abrupt steering movements that can cause skidding.

• Turn on wipers: Fog forms a water film on the windshield, further impairing visibility.

• Use proper lighting: Use low beams during the day when foggy. Use fog lights only if visibility drops below 50 meters. Never use high beams—they worsen visibility by reflecting off fog.

• Stay alert: Watch for brake lights and obstacles ahead.

• If you break down or crash:

  • Turn on your hazard lights immediately.

  • Pull over to the breakdown/emergency lane.

  • Exit the vehicle and stand behind the guardrail.

  • Call the police.

  • Retrieve the warning triangle.

  • Walk against traffic while waving the triangle and place it far enough from your car to warn others.

Technological Assistance

Modern driver-assistance systems can make driving in fog safer. Here are some helpful technologies:

• Automatic lighting: Newer cars often have adaptive lighting systems that adjust headlights depending on time and weather. If fog is present during the day and the system doesn’t switch to low beams, do it manually.

• Cornering lights: These lights swivel in the direction of the turn, making corners safer in poor visibility.

• Adaptive cruise control: It adjusts your speed to road conditions, helping avoid unintentional speeding.

• Lane-keeping assist: Warns you if you're drifting out of your lane—even in poor visibility.

• Adaptive braking and stability control: Helps prevent skidding and improves braking on slippery surfaces.

• Camera systems: Provide better visibility in low light and foggy conditions.

Conclusion

At CARIFY, we want you to always arrive at your destination safely. Our safety measures for driving in fog are meant to serve as a guiding light through even the thickest fog. Here’s what’s especially important:

• Ease off the gas: Drive at an appropriate speed (visibility in meters = speed in km/h)!

• Keep your distance: Expect sudden braking from other drivers, delayed reaction times, and slippery roads (minimum distance = your current speed)!

• Use the right lighting: Even during the day, use low-beam headlights when driving in fog. High beams are a no-go. Fog lights are only permitted when visibility is less than 50 meters.

• Use modern driver assistance systems: Lane-keeping assist, adaptive lighting, braking assist, and similar technologies improve your safety in foggy conditions.

• Stay informed about traffic regulations and follow them. This is especially important for speed limits.

You’ll be especially safe with CARIFY subscription cars: they’re in excellent condition, usually equipped with the latest assistance systems, and always fitted with seasonal tires that have good tread.