The easiest way to calculate the approximate reaction distance is by rounding the speed to the nearest ten, taking away the zero and multiplying by three.

Examples

• 30 km/h: 3 × 3 = 9 metres
• 52 km/h: 5 × 3 = 15 metres
• 77 km/h: 8 × 3 = 24 metres
• 94 km/h: 9 × 3 = 27 metres
• 110 km/h: 11 × 3 = 33 metres

The formula is based on a driver who reacts in one second, which is the average reaction time. If the reaction time is two seconds, the reaction distance becomes twice as long.

Read more about the reaction, braking and stopping distance