Which shape signifies an actual railroad crossing?

The crossbuck sign is specifically designed to signify an actual railroad crossing. This shape consists of a white rectangular sign with the words "RAILROAD CROSSING" printed in black. When approaching a railroad crossing, the presence of a crossbuck indicates that drivers should slow down, be alert, and prepare to stop if a train is approaching.

While other shapes are used for various traffic signs, none convey the same message as the crossbuck. For instance, circular signs usually indicate a railroad crossing warning but do not indicate the crossing itself; triangular shapes are typically used for yield signs, and square signs are more common for regulatory or informational purposes. The crossbuck's unique design makes it easily recognizable and helps ensure that drivers take the necessary precautions when approaching a railroad.