What safety requirement should be followed when coupling cars on a grade?

When coupling cars on a grade, the safest practice is to ensure that cars are moved upgrade. This is crucial because moving cars upgrade reduces the risk of them rolling back down the slope unintentionally. Coupling cars downhill or at high speed poses significant hazards, as the gravity can lead to a loss of control during the coupling process, increasing the likelihood of accidents or injuries.

By moving the cars upgrade, the operator can effectively manage the weight and momentum of the cars, ensuring a safer coupling procedure. This technique minimizes the chances of a sudden rollback and creates a more stable environment for the task at hand. Additionally, coupling on flat ground is generally preferred whenever possible, as it allows for better control. However, if a grade is unavoidable, the requirement to move upgrade is a critical safety measure.