After releasing the independent brakes, what is the next step in the air brake test process?

The next step in the air brake test process after releasing the independent brakes is to make a 10 psi brake pipe reduction using the automatic brake valve. This action is crucial as it ensures that the train's air brake system is functioning correctly and that the brake pipe pressure is effectively monitored.

Making a 10 psi reduction activates the brakes and allows for the assessment of the system's responsiveness. It also provides a clear indication of whether the automatic brake system holds pressure correctly and applies the brakes as expected. This step is a vital part of verifying the integrity of the brake system as it checks for any potential leaks or issues in the system that might prevent safe operation.

The other options would not follow logically after releasing the independent brakes. For example, fully applying independent brakes would not be the next step as it assumes the need for additional brake application rather than checking system integrity. Observing gauges for leakage is an important part of the process, but it follows the pressure reduction because the gauge readings would reflect changes only after the reduction is made. Cutting the automatic brake valve in would typically be part of the initial setup and not a sequential step in verifying the brake system's functionality after the brakes are released.