What technique is used to determine if brakes reapply after releasing air pressure?

The technique used to determine if brakes reapply after releasing air pressure is through the activation of the automatic brake valve. This involves engaging the automatic brake system and observing the behavior of the brakes in response to changes in air pressure.

When the automatic brake valve is activated and air pressure is released, it allows the system to automatically apply the brakes. This function is critical in ensuring that the train braking system is responsive and effective. When pressure is released, the brake cylinders must be checked for their ability to reapply; this indicates whether the brakes are functioning correctly.

While techniques such as independent brake checks, visual inspections, and pressure gauge observations can provide valuable information regarding the condition of the braking system, they are not specifically designed to test the reapplication of the brakes in response to a release of air pressure as effectively as the activation of the automatic brake valve. This makes the automatic brake valve activation the most reliable method among the choices presented for confirming brake functionality after air pressure changes.