Not quite!

Q: You're driving in fog. When should you switch on your rear fog lights?
Correct answer:
When visibility has fallen to 100 metres (328 feet) or less
Explanation
If visibility falls below 100 metres in fog, switching on your rear fog lights will help road users behind to see you. Don't forget to turn them off once visibility improves: they're very bright, so they might be mistaken for brake lights and they could dazzle other drivers.
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