Assuming good traction and constant vehicle weight, if you double your speed, your vehicle's braking distance will be
- doubled.
- eight times as long.
- tripled.
- quadrupled. ✓
Answer: D. quadrupled.
If you double your speed, your braking distance becomes quadrupled — four times as long.
Why this is the answer
The handbook's speed and weight facts say that doubling vehicle speed requires four times the stopping power. Speed is the only thing changing in this question, since weight stays the same and traction is good, so the same doubling relationship applies: twice the speed means four times the stopping demand and four times the distance covered while you shed that speed. The handbook also notes that doubling only the weight calls for twice the stopping power, which shows the speed effect is the stronger of the two.
Why the other answers are wrong
- A. doubled. — Doubling would mean the stopping demand grows only in step with speed, but the handbook links a doubled speed to four times the stopping power, not two.
- B. eight times as long. — Eight times is what the handbook gives when both speed and weight are doubled, and here the weight is held constant.
- C. tripled. — Tripling does not match the handbook's figure at all; doubling speed produces four times the stopping power, not three.
Remember it
Think of it as speed counting twice: double the speed and the stopping demand goes up by two times two.