Our tips for driving in foggy weather

Fog is a weather phenomenon that can represent a real danger for motorists. It reduces visibility and increases the risk of serious accidents. To avoid such situations, drivers must adapt their driving style to their environment. Road safety rules also recommend using appropriate vehicle equipment.
Our tips for driving in foggy weather

Road rules: use of lights in fog

Rules 234-236 of the Highway Code details the use of fog lamps. The Road Vehicles Lighting Regulations 1989 states a clear distinction regarding the legal requirements for using headlamps and front fog lamps.

Rear fog lights are a legal requirement for UK vehicles on the roads, whereas front fog lights are optional. Although it’s not mandatory to use your fog lights while driving in fog, it’s much safer. Front fog lights can supplement or replace beam headlamps in fog, heavy rain or snowfall during the daytime hours. They are also indicated in addition to the main-beam headlamps when visibility is poor. When visibility improves, turn the fog lamps off as soon as possible to avoid dazzling other drivers. Switch to your dipped-beam headlamps to ensure you remain visible when driving in dull weather.

At the rear, the fog lamp(s) indicates a vehicle in use when there is fog or snowfall.

Please note: fog lights first appeared on most modern vehicles in the 1990s and are compulsory on all cars driving UK roads. They are not compulsory throughout France and other European regions. Correct use is mandatory, but on the other hand, an abuse of their use exposes the driver to a fine.

What are the recommendations for driving in fog?

Before entering the fog, check your mirrors and slow down. If the road is clear, but the word ‘Fog’ is on a roadside signal, be prepared for a drifting patch or bank of fog ahead. Entering a foggy layer can surprise drivers when suddenly thick fog causes the loss of visibility. In such cases, following the recommendations of the Highway Code helps reduce accidents as much as possible.

Warning: never use your fog lights when it is clear and visible, especially at night when other drivers can easily be dazzled. It is both dangerous and illegal.

Driving speed in fog

Whether travelling on mountain roads or motorway, when dense fog appears, drivers should reduce speed to less than 50 km/h. Deceleration should be gradual, especially if the associated speed is high and traffic is heavy. Keep a safe distance from vehicles in front of you. The usual safety distance of two strokes between vehicles is only sufficient when driving at appropriate speeds. Rear lights can provide a false sense of security. You should be able to pull up well within the distance you can see clearly, which is particularly important on motorways and dual carriageways where vehicles travel faster. Don’t accelerate too quickly to get away from other moving vehicles that are close behind you. Always check your mirrors before slowing down, and use your brakes so that your brake lights indicate to other drivers that you are slowing down.

Warning: overtaking is prohibited when visibility is less than 50 metres, including on motorways. This distance corresponds to the line, plus the marked spaces on hard shoulders.

Adapt your driving behaviour

The best way to avoid taking risks in case of fog is to postpone your departure; for example, wait for the sunrise or an increase in temperature that favours dispersion. However, when this is not possible or when fog sets during a journey, you can keep yourself and other road users safe by:

  • switching on fog lights if it is not raining;
  • maintaining a low and steady speed, without slowing down too much;
  • using the white lines as a visual cue rather than the vehicle in front;
  • maintain an appropriate safety interval in the event of emergency braking;
  • do not overtake and stay in your lane;
  • be extra vigilant;
  • pay attention to the possible appearance of ice with freezing fog;
  • opening the window at intersections to better distinguish approaching vehicles.

Please note: high-beam fog headlamps create a dazzling optical effect that is dangerous to approaching drivers and also for their users. Fog or dipped-beam headlights must replace them.