What must be known before coupling to or moving cars?

Before coupling to or moving cars, it is crucial to verify that the cars and engines are properly secured. This step is essential for safety and operational efficiency. Ensuring that the equipment is secure helps prevent accidents, such as unintended movements that can cause derailments or injuries to personnel. Properly secured cars and engines mean that the brakes are engaged and that there are no loose items that could pose hazards during the coupling or moving process.

Each of the other options lacks the necessary focus on safety and readiness. Knowing the speed of the cars does not address the critical safety protocols needed when coupling; the color of the cars is irrelevant to their operation; and while understanding the type of load may provide useful context, it does not supersede the importance of ensuring the equipment is secure. Hence, verification of security is the most critical information needed before proceeding.