What does ABS (anti-lock braking system) do during hard braking?

An anti-lock braking system (ABS) rapidly pulses the brakes to prevent the wheels from locking up during hard or emergency braking. Locked wheels skid and lose steering control; by keeping the wheels rotating, ABS lets the driver continue to steer while braking hard and helps maintain traction, especially on slippery surfaces. ABS does not necessarily shorten stopping distance, but it improves control. The driver should apply firm, steady pressure (not pump the pedal) and may feel the pedal pulsate when ABS activates. Knowing ABS prevents wheel lockup to preserve steering is common brake-system content.