Driving in foggy conditions

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Check the weather forecast

Before you travel in severe weather conditions, keep up to date with the latest about what to expect.

Fog affects driver perception

Fog can drastically reduce your visibility to other road users and of course, theirs to you.

One moment you can be driving in good conditions and then suddenly encounter fog – you might not see it coming.

Be careful: even when the fog seems to be clearing up, you can find yourself back in the thick of it in a matter of seconds.

Hey did you know?

Fog is made up of tiny water droplets all suspended in what is essentially a cloud on the ground which contains up to 0.5 ml of water per cubic metre.

To visualise this, if you were to fill an Olympic sized swimming pool with fog and then somehow condense it, you would be left with around 1.25 litres of water (or just over 2 pints).

The best advice if you are driving in fog

The Highway Code states that when driving in fog, you MUST use your headlights if your visibility is down to 100m or less. Also, use your fog lights, but remember to switch these off as soon as visibility improves.

  • Following a car’s rear lights can be comforting but can also give you a false sense of security. Make sure you keep a safe distance between you and the car in front.
  • When slowing down be aware it may only be your brake lights that are warning drivers behind you that you are slowing down. Nor may they be able to see anything else, so use your brakes with that in mind.
  • Drive at a speed that allows you to pull up within the distance you can see clearly, particularly on motorways and dual carriageways as you will be travelling faster.
  • Be aware of other drivers not using headlights.
  • At junctions only emerge when you are sure it is safe to do so. If necessary, wind down your window and listen out to confirm the way is clear and don’t hesitate once you are in a position that is directly in the path of oncoming traffic.
  • Don’t forget to use your windscreen wipers and the demister.


Driving with your fog lights on when you can see further than 100m ahead of you is illegal. Make sure you switch them off if the fog clears, or switch to headlights if there’s still thick fog on the road.