The MU-2A valves on trailing locomotives in a consist should be in which position?

In a train consist, the MU-2A valves on trailing locomotives must be set to the "Trail" position to ensure proper air brake operation and control. When the MU-2A valve is in the Trail position, it allows the air brake system of the trailing locomotive to function as part of the entire train's braking system, while preventing it from taking control of the brake system independently.

When in the Trail position, the trailing locomotive will effectively follow the commands given by the lead locomotive, ensuring that the entire train stops uniformly and efficiently in response to braking signals. This is vital for maintaining safety and control of the entire train, especially during operations like stopping or slowing down.

Setting the valve to any other position, such as Lead, Off, or On, would disrupt the intended communication and control between the locomotives in the consist, potentially leading to ineffective braking or loss of control under some conditions. Therefore, the proper setting of the MU-2A valve in trailing locomotives is crucial for seamless operational integrity across the entire train.