It is important to be able to:
The diagram shows some typical stopping distances for an average car in normal conditions.
Travelling at 20 mph (32 km/h):
Travelling at 40 mph (64 km/h):
Travelling at 70 mph (112 km/h):
It is important to note that the thinking distance is proportional to the starting speed. This means that it increases proportionally as speed increases – ie if speed doubles, thinking distance also doubles. However, the braking distance increases by a factor of four each time the starting speed doubles.
For example, if a car doubles its speed from 30 mph to 60 mph, the thinking distance will double from 9 m to 18 m and the braking distance will increase by a factor of four from 14 m to 56 m.