Assuming good traction and constant vehicle weight, if you double your speed, your vehicle's braking distance will be
- quadrupled. ✓
- doubled.
- eight times as long.
- tripled.
Answer: A. quadrupled.
If you double your speed with good traction and constant weight, your braking distance is quadrupled.
Why this is the answer
The handbook passage says that as vehicle speed rises, stopping distance grows faster than the speed change. It gives the specific example that when speed is doubled, stopping distance increases by four times. Since the question keeps traction good and vehicle weight constant, speed is the factor being changed, so the braking distance becomes four times as long.
Why the other answers are wrong
- B. doubled. — Doubling is too small because the handbook says stopping distance rises faster than speed, giving four times the distance when speed doubles.
- C. eight times as long. — Eight times is what the passage gives when both vehicle weight and speed are doubled, not when speed alone is doubled.
- D. tripled. — Tripling is not supported; the handbook's example for doubled speed is four times the stopping distance, not three times.
Remember it
Think of the road stretching out four times when your speed goes up twice.