Which statement is true regarding the air braking system?

The air braking system in commercial motor vehicles relies on compressed air to engage brakes effectively. One of the critical aspects of this system is that it requires the driver to actively apply pressure to the service brake pedal for the system to function and decelerate the vehicle. When the driver presses the brake pedal, it activates the air supply that then engages the brakes, allowing for controlled stopping.

The system is designed this way to provide the driver with direct control over the vehicle’s speed and stopping power, making it essential for safe driving practices. This relationship between the driver’s input and the braking action is fundamental to the operation of air brakes, ensuring that braking is responsive and effective based on the driver's commands.

Other options present misconceptions about how the air braking system functions, such as operating under low air pressure or being unaffected by the driver's input. In reality, the system requires sufficient air pressure to work correctly, and it is directly reliant on the driver's actions to engage the brakes.