Driving in fog: which lights to use, speed and when to switch fog lights off
Fog closes in and you can see about 60 metres. Choose the right lights and speed, keep back from the tail lights ahead and know when to switch your fog lights off.
The short version
- Under about 100 metres: dipped headlights on, fog lights allowed. Never full beam.
- Drive so you can stop well within the distance you can see. Do not hang on to tail lights.
- Switch fog lights off as soon as the fog clears.
Step 1
Fog closes in. You can see about 60 metres.
Which lights should you have on?
✓ Dipped headlights, and fog lights because you cannot see 100 metres. Under about 100 metres you must use headlights and you may add fog lights so others see you sooner.
Why not the other options
- ✗ Full beam, so you can see further. Full beam bounces back off the fog and makes it harder to see. Use dipped headlights.
- ✗ Hazard warning lights while you drive. Hazard lights are for when you are stopped. Other drivers read them as a broken-down car.
- ✗ Sidelights only, so you do not dazzle anyone. Sidelights are too weak to be seen in fog. You must use headlights when visibility is this poor.
Step 2
You are doing 40 mph and the road ahead disappears into grey.
How fast should you drive?
✓ Check your mirror, then slow down so you can stop well within the 60 metres you can see. Anything could be just inside the fog. At 40 mph you need about 36 metres to stop on a dry road, and this road is wet.
Why not the other options
- ✗ Keep to the speed limit as long as the road looks empty. The limit is a maximum, not a target. You cannot tell the road is empty past 60 metres.
- ✗ Hold 40 mph, the fog may clear soon. Fog often gets thicker without warning. Drive for what you can see now.
- ✗ Brake hard straight away. A car behind may not see you in time. Check your mirror and slow down smoothly so your brake lights warn them.
Step 3
A pair of red lights appears ahead. The car in front is braking.
How close should you follow it?
✓ Drop back so you could stop if it stopped suddenly. In fog you see less and react later. Leave more room than usual, at least the gap you could stop in.
Why not the other options
- ✗ Close enough to keep its tail lights in view. Following tail lights feels safe but it is a trap. If that car stops sharply you will hit it.
- ✗ Overtake it so you have a clear road. You cannot see oncoming traffic in fog. A van is coming the other way.
- ✗ Flash your headlights so it speeds up. The driver ahead is driving for the conditions. Flashing only distracts them.
Step 4
A car is right on your tail, its headlights filling your mirror.
What do you do?
✓ Keep a steady speed, leave more room ahead and slow down early and gently. A bigger gap in front gives you time to brake gently, so the driver behind is not caught out.
Why not the other options
- ✗ Speed up to get away from them. The Highway Code says do not accelerate away from a driver too close behind in fog. You would just be going too fast.
- ✗ Tap your brakes to warn them off. Sudden braking invites a crash from behind. Stay steady and leave more room ahead instead.
- ✗ Turn round to see how close they are. Your eyes belong on the road ahead, especially in fog. Use your mirrors.
Step 5
The fog lifts. You can now see well over 100 metres.
What about your fog lights?
✓ Switch them off now. Once you can see over 100 metres fog lights only dazzle others and can hide your brake lights. Switching them off is the law.
Why not the other options
- ✗ Leave them on in case the fog comes back. You must switch them off when visibility improves. Turn them back on if the fog returns.
- ✗ Switch off your headlights too, it is daytime. Keep dipped headlights on while it is still misty. It helps others see you.
- ✗ Leave them on, they make you safer. A rear fog light is very bright. In clear air it dazzles the driver behind and makes your brake lights harder to spot.
The rules behind it
- Rule 226 You MUST use headlights when you cannot see more than about 100 metres. You may use fog lights then, but you MUST switch them off when visibility improves.
- Rule 116 Hazard warning lights are for when you are stopped and causing a temporary obstruction. You MUST NOT use them while driving, except briefly on a motorway or unrestricted dual carriageway to warn of a hazard ahead.
- Rule 234 Before entering fog, check your mirrors and slow down.
- Rule 235 In fog, be able to stop well within the distance you can see, keep well back from the car in front, do not accelerate away from a driver too close behind, and check your mirrors before you slow down.
- Rule 126 Leave enough space to stop safely if the vehicle in front suddenly slows down or stops. Never get closer than the overall stopping distance.
- Rule 236 You MUST NOT use fog lights unless visibility is seriously reduced. They dazzle others and can hide your brake lights, so switch them off when the fog clears.
More situations
Based on the Highway Code and the Road Traffic Act 1988 as published on GOV.UK in October 2026, in our own words; follow the links for the full text. Insurance points are common UK insurer policy terms, so check your own policy. This is not legal advice. Contains public sector information licensed under the Open Government Licence v3.0.