What does an ABS system do?
- It shortens stopping distance.
- It brakes automatically when needed.
- It increases braking power.
- It prevents wheel lock. ✓
Answer: D. It prevents wheel lock.
An ABS system prevents wheel lock.
Why this is the answer
The handbook says ABS is added to a normal air brake system to reduce wheel lockup and skids when you overbrake on a slippery surface. When a wheel locks, the system releases air pressure at that wheel and then lets the brakes reapply, repeating as needed. This lets you brake hard without skidding and keep steering control. The same passages say ABS does not let you stop sooner; on gravel the distance may even be longer.
Why the other answers are wrong
- A. It shortens stopping distance. — The handbook says ABS does not let you stop sooner, and on gravel the braking distance may be longer.
- B. It brakes automatically when needed. — ABS does not brake for you; the handbook says you must apply and hold firm pressure on the brake pedal for it to work.
- C. It increases braking power. — ABS releases and reapplies air pressure to control wheel lock, rather than increasing the braking power itself.
Remember it
Think of ABS as keeping the wheel rolling, not squeezing harder; you still need firm pedal pressure.
Official handbook: ICBC Driving Commercial Vehicles, 2 Heavy vehicle braking – Braking, p. 25