Commercial Driver’s License (CDL) Practice Exam

The primary purpose of the service brake system is to apply and release the brakes using the brake pedal. This system is crucial for safely slowing down or stopping the vehicle as needed while driving. When the driver presses the brake pedal, the service brakes activate to reduce the speed of the vehicle or bring it to a complete stop. This function is essential for normal driving operations and responding to traffic conditions.

While other options relate to braking systems, they serve different functions. For instance, engaging anti-lock brakes is a safety feature that helps prevent wheel lock-up during hard braking, but it does not represent the fundamental purpose of the service brake system. Energy recovery is associated with certain hybrid systems and does not pertain to the service brakes in standard truck operations. Controlling wheel speed during heavy loads is important but is typically managed through different systems like transmission control rather than the service brake system itself.