Final answer:
If a railroad grade crossing has no warning devices or only a cross buck sign, drivers should exercise caution, slow down, look both ways, listen for approaching trains, and come to a complete stop at a safe distance from the tracks before proceeding.
Step-by-step explanation:
If a railroad grade crossing has no warning devices or only a cross buck sign, it means that there are no active warning signals such as flashing lights or gates to alert drivers of an approaching train. In such a situation, drivers should exercise caution and be prepared to stop. They should slow down, look both ways, and listen for any approaching trains.
If they see a train coming, they should come to a complete stop at a safe distance from the tracks, allowing the train to pass before proceeding.