DVSA Speed and Stopping Distances

Question 1

What is the overall stopping distance at 30 mph in dry conditions?

Accepted Answer

23 metres (75 feet)

Answer

At 30 mph, the overall stopping distance is approximately 23 metres (75 feet). This comprises 9 metres (30 feet) thinking distance and 14 metres (45 feet) braking distance. This is roughly 6 car lengths.

Question 2

What two components make up the overall stopping distance?

Accepted Answer

Thinking distance and braking distance

Answer

Overall stopping distance = thinking distance + braking distance. Thinking distance is the distance travelled while you recognise the hazard and begin to brake. Braking distance is the distance covered from when the brakes are applied until the vehicle stops.

Question 3

At 70 mph, what is the approximate overall stopping distance?

Accepted Answer

96 metres (315 feet)

Answer

At 70 mph, the overall stopping distance is approximately 96 metres (315 feet) — about 24 car lengths. The thinking distance is 21 metres and the braking distance is 75 metres. At higher speeds, braking distance increases disproportionately.

Question 4

How does doubling your speed affect your braking distance?

Accepted Answer

It roughly quadruples

Answer

Braking distance increases with the square of the speed. If you double your speed from 30 to 60 mph, your braking distance approximately quadruples — from 14 metres to 55 metres. This is because kinetic energy increases exponentially with speed.

Question 5

What happens to your stopping distance in wet conditions?

Accepted Answer

It can at least double

Answer

In wet conditions, the overall stopping distance can at least double because the road surface has less grip. At higher speeds, the risk of aquaplaning also increases. You should reduce speed and at least double your following distance.

DVSA UK Driving Theory Practice Test

DVSA UK Driving Theory Practice Test

DVSA Speed and Stopping Distances