What is the function of the independent brake valve handle during the process of adding helpers?

The function of the independent brake valve handle during the process of adding helpers is to release the helper locomotive's brakes. When additional locomotives are attached to a train, it is essential for the brakes on these helpers to be released so that they can contribute to the train's movement effectively.

Using the independent brake valve handle allows the engineer to control the braking of individual locomotives separate from the train brake system. This enables the engineer to ensure that the helper locomotives are free to assist without interference from their own brakes. Properly managing this aspect of train handling is crucial for safety and efficiency when integrating additional power into a train.

Other options, while related to braking functions, do not accurately describe the purpose of the independent brake valve handle in this specific context. A full brake application would not be appropriate when adding helpers, as it would impede the ability of the locomotives to assist. Locking the brake system is not needed at this stage, and initiating a brake pipe test pertains to a separate procedure focused on ensuring the integrity of the air brake system rather than managing the individual locomotives’ brakes.