Final answer:
The cross-buck sign is a road sign used at level crossings to warn road users of trains. It is a white X-shaped cross with the words "RAILROAD CROSSING". The purpose of the sign is to alert drivers and pedestrians to stop, look, and listen for an approaching train.
Step-by-step explanation:
The cross-buck sign is a type of road sign used in railway operation. It is typically placed at level crossings to warn road users of the potential presence of trains. The sign consists of a white X-shaped cross with the words "RAILROAD CROSSING" in black lettering. The purpose of the cross-buck sign is to alert drivers and pedestrians to stop, look, and listen for an approaching train before crossing the railroad tracks.