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The three-second rule

Keep at least three seconds to the car in front in good conditions. Pick a fixed point such as a sign. When the car in front passes it, count slowly to three. If you reach the point before you finish, you are too close. On slippery roads, in the dark and in rain the gap should be much larger.

d = v \cdot 3\ \text{s}

three-second gap in metres with speed in m/s

Symbols

$d$	distance to the car in front	m
$v$	speed	m/s

Example

At 80 km/h, $v \approx 22.2$ m/s.

Three seconds gives $d \approx 22.2 \cdot 3 \approx 67$ m.

A gap in seconds works at every speed. A gap in metres must grow with speed.

Practise speed, distance and stopping distance for free →

← Stopping distance · Speed limits →

Part of Car licence (class B): Speed, distance and stopping distance.