How should you verify that the spring brakes engage when air pressure drops below a specific level?

To verify that the spring brakes engage when air pressure drops below a specific level, it's essential to park on level ground, release the parking brake, and press the brake pedal. This method effectively tests the behavior of the air brake system under a controlled condition where you can observe the engagement of the spring brakes.

When doing this, if the air pressure falls below the manufacturer's specified threshold, the spring brakes should engage automatically. This is a critical safety feature designed to prevent the vehicle from rolling or moving unexpectedly when air pressure drops. Ensuring that the spring brakes engage allows the driver to confirm that the fail-safe mechanism is operational and functioning as intended.

Other choices do not adequately test the spring brakes' engagement. Checking tire pressure relates to vehicle safety but does not directly address the spring brake function. Monitoring the air compressor gauge is useful for understanding overall system pressure but does not provide a direct test of the spring brakes. Adjusting brake pedal tension might affect the brake's feel or operation but does not verify whether the spring brakes engage in a low-pressure scenario.