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

An anti-lock braking system (ABS) is designed to prevent the wheels from locking up during hard braking. This is crucial because when wheels lock, the vehicle can skid and lose traction, making it difficult to steer. By electronically monitoring the speed of each wheel, ABS can adjust brake pressure instantaneously. If it detects that one or more wheels are about to lock up, it automatically reduces the brake pressure to those wheels, allowing them to continue rotating. This enhances control over the vehicle, improves steering ability in emergency situations, and ultimately helps shorten stopping distances on slippery surfaces.

The other options do not accurately describe the function of ABS. For instance, locking the wheels during hard braking would cause loss of control rather than improve braking performance. Adjusting the vehicle's speed automatically is not a function of ABS; rather, it aims to maintain wheel rotation. Similarly, enhancing tire tread does not relate to the braking system but rather focuses on tire design and maintenance. Thus, the description provided aligns with the core function of ABS, which is to maintain vehicle control under braking conditions.