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Following distance and braking

The check asks how much space to keep behind the car ahead and how a car stops. Japanese law gives no fixed number of metres on ordinary roads: the gap must be enough to avoid a crash if the car ahead stops suddenly.

Key rules

• Keep a gap that lets you avoid hitting the car ahead even if it stops suddenly.
• Stopping distance is reaction distance plus braking distance.
• When you are tired, you notice danger later, so the reaction distance gets longer.
• On a wet road, or with a heavy load, the braking distance gets longer.
• On a wet road with worn tyres, stopping distance can be about twice as long as on a dry road with good tyres.
• Consider weather, road, tyres and load when you choose the gap. Leave a wider gap on downhill roads.
• Start braking lightly, then press harder. Use the brake in several steps.
• Do not brake hard unless you must to avoid danger.
• Do not cut in front of another car suddenly or squeeze a car beside you.

Numbers to remember

Common traps

• "Keep exactly X metres" on an ordinary road is not in the law. The rule is: enough to avoid a crash.
• Obeying the speed limit does not mean your gap is enough.
• Braking distance alone is not stopping distance. Reaction distance is added.
• "Sudden braking is always forbidden" is too strong: it is allowed when needed to avoid danger.
• The 100 m and 80 m figures are expressway guides for dry roads. They are not a rule for all roads.

Some countries teach a time gap, such as 2 seconds. Japanese rules say the gap must be enough to avoid a crash, and give metre guides only for expressways.

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