What is required before proceeding after adding cars during a transfer train movement?

Before proceeding after adding cars during a transfer train movement, it is crucial to verify that the brake pipe pressure is restored. This step is essential because proper brake function is critical for the safe operation of any train. If the brake pipe pressure is not restored, the braking system may not function correctly, which could lead to dangerous situations, especially with the additional weight and potential complexities introduced by the new cars.

By confirming that the brake pipe pressure is at the required level, the crew ensures that the entire train will have the necessary braking force to stop safely when needed. This verification is a crucial part of maintaining safety standards during train operations.

The other factors, while they might be important in different contexts or situations, do not specifically address the immediate safety concerns involved in confirming the readiness of the train's braking system after modifications.