What is the procedure when detaching locomotives from a train?

The procedure when detaching locomotives from a train involves making a 20 psi brake pipe reduction after securing the equipment. This step is crucial for ensuring that the air braking system is adequately prepared for the disconnection process. The reduction in brake pipe pressure allows for a safe release of the locomotives from the train without causing any potential damage or safety hazards.

When the brake pipe pressure is reduced, it helps to prevent any unforeseen movement of the train while performing the detachment, as it effectively releases the brake system's hold on the locomotives. This procedure is part of the safety protocols that ensure both the train and the crew are protected during operations.

In contrast, only releasing hand brakes does not provide the necessary control or safety as it may not address the full function of the air brake system. Checking all air pressures before detaching could be important but is not the primary procedure during the detachment. Leaving air brakes engaged until reconnecting would not be advisable as it could lead to complications when it comes time to reattach the locomotives or create an unexpected situation in the tight coupling of train cars.