What is the primary function of ABS (Anti-lock Braking System) in braking performance?

• A. To increase braking pressure on all wheels regardless of conditions.
• B. To monitor wheel speed and modulate brake pressure to prevent wheel lock.
• C. To lock tires to improve stopping distance.
• D. To monitor wheel speed and modulate brake pressure to prevent wheel lockup.

Answer: (D)

ABS is designed to keep the wheels from skidding during hard or emergency braking by watching each wheel’s speed and quickly adjusting the brake pressure at individual wheels. When a wheel starts to slow enough that it could lock up, the system relieves and then reapplies pressure in very rapid pulses. This prevents a complete skid, helping you maintain steering control and reduce stopping distance on slippery or uneven surfaces.

The precise way this is stated is to monitor wheel speed and modulate brake pressure to prevent wheel lockup. That term “lockup” is the technical way to describe the dangerous condition ABS fights against, where a wheel stops rotating while the vehicle is still moving. The other ideas don’t fit: increasing pressure on all wheels regardless of conditions would push wheels into lock, not away from it; locking tires would defeat steering and usually lengthen stopping distance; and while monitoring speed and modulating pressure is correct, the standard wording uses “lockup,” making the chosen description the clearest, most accurate way to express the function.