What happens if the service brake is activated while the permanent brake is switched on?

When both the permanent brake and the service brake are activated, the braking force on the drive axle wheels increases, resulting in stronger braking. The permanent brake provides a continuous braking effect to maintain vehicle stability, especially on slopes, while the service brake adds additional braking power when the driver presses the brake pedal. Importantly, the permanent brake does not switch off automatically, and the wheels do not lock under normal conditions, preventing skidding and maintaining control. Understanding this helps ensure smooth and safe braking in vehicles equipped with these systems.