You are travelling at 30 km/h. According to the rule of thumb, the braking distance is 9 metres when braking normally. How long is the braking distance under the same conditions when travelling at 60 km/h?

When you double your speed, the braking distance increases by the square of that factor. Since you are traveling at 30 km/h with a braking distance of 9 meters, increasing the speed to 60 km/h (which is double) means the braking distance becomes 4 times greater (2 squared = 4). Therefore, 9 meters times 4 equals 36 meters. This rule highlights how braking distance grows much faster than speed, emphasizing the need to adjust driving speed carefully.