Safety margins: what you need to know

Key points: safety margins

1. Overall stopping distances in good conditions: about 23 m at 30 mph, 36 m at 40, 53 m at 50, 73 m at 60 and 96 m at 70 mph (rule 126).
2. Stopping distance is thinking distance plus braking distance, and both grow with speed.
3. In the wet, stopping distances at least double, so leave at least a four-second gap (rule 227).
4. On ice they can be up to ten times longer, so slow right down (rule 126).
5. In fog, slow down, keep well back and use dipped headlights, adding fog lights only below 100 metres (rule 235).
6. After driving through deep water, test your brakes gently to dry them before you need them (rule 121).

Now test yourself on safety margins

9 questions on this topic, with the answer and the cited rule shown the moment you choose. If you miss any, the points above are where to look.

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