Speed and Stopping Distances Flashcards

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

Answer: 23 metres (75 feet)

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.

What two components make up the overall stopping distance?

Answer: Thinking distance and braking distance

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.

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

Answer: 96 metres (315 feet)

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.

How does doubling your speed affect your braking distance?

Answer: It roughly quadruples

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.

What happens to your stopping distance in wet conditions?

Answer: It can at least double

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.

What is the thinking distance at 60 mph?

Answer: 18 metres (60 feet)

At 60 mph, the thinking distance is approximately 18 metres (60 feet). A simple rule of thumb is that thinking distance in feet roughly equals the speed in mph multiplied by one — so 60 mph equals about 60 feet of thinking distance.