Final answer:
The best action for the train operator is to wake the customer and ensure his safety, following company protocols if further assistance is required.
Step-by-step explanation:
The question involves a train operator responding to finding an asleep customer on a train that has been moved to a yard. The best action for the train operator would be to gently wake the customer and inform him of the situation ensuring his safety as the train is no longer in service.
This action demonstrates professional etiquette and responsibility in handling matters concerning passengers. If the train operator is unable to wake the customer or if the customer needs assistance, the train operator should follow the company's protocols, which might involve calling for medical assistance or contacting security to ensure the person's well-being.