How do you drive safely in fog?
Why pileups happen in fog specifically
The road feels empty, so the instinct is to keep normal pace. But everyone ahead is doing the same, and the first vehicle to brake becomes invisible until it is metres away. Multi-vehicle collisions in fog are almost always a chain of drivers who each had too little time.
The rule that prevents it is simple and unnatural: your speed must let you stop within the distance you can actually see.
Where and when fog forms
Radiation fog forms on clear, calm nights as the ground loses heat — which is why it appears around dawn and burns off mid-morning as the sun warms the surface.
It settles in valleys, along riverbanks and on low-lying roads, because cold air sinks. A clear hilltop tells you nothing about the dip ahead, and that transition is where drivers are caught out.
If you have to stop
Leave your lights on and get behind a barrier if there is one. And open a window: you will hear approaching traffic long before you see it, which is the only early warning available.
Step by step
- Switch to dipped beams and fog lights
Full beams actively reduce what you can see. - Slow to a speed you can stop within your sight line
In dense fog that can be under 50 metres — genuinely slow. - Increase your following distance well beyond normal
Brake lights are the only warning you will get, and they appear late. - If it becomes too thick, pull off the road completely
Into a car park or side road — never the hard shoulder, where stationary vehicles get struck.
