Assuming good traction and constant vehicle speed, if you double your vehicle's weight, your vehicle's braking distance will be
- tripled.
- quadrupled.
- eight times as long.
- doubled. ✓
Answer: D. doubled.
Doubling your vehicle's weight will double your braking distance, assuming good traction and constant speed.
Why this is the answer
The Air Brake Handbook passage says stopping distance increases in proportion to any increase in vehicle weight, and its diagram labels doubling vehicle weight as doubling stopping distance. With traction good and speed held constant, the only change is the weight, so the brake system must do more work but the distance grows in that same proportional way. That supports the doubled result rather than a larger multiplier.
Why the other answers are wrong
- A. tripled. — Tripling is not supported; the handbook ties a weight increase to a proportional increase in stopping distance, so twice the weight means twice the distance, not three times.
- B. quadrupled. — Quadrupling applies to doubling speed, not to doubling weight while speed is held constant.
- C. eight times as long. — Eight times is the handbook's result when both vehicle weight and speed are doubled together, not when weight alone is doubled.
Remember it
Pair weight with an even scale in your mind; don't borrow the speed multiplier.