If it is a four-way stop, wait your turn. In any case, you must wait until a safe interval occurs. Triangle signs mean yield. You must slow down to a speed that is reasonable for existing conditions and stop if necessary. If you must stop, do so at a marked stop line, if it exists.
Round signs mean railroad crossing.
This sign is posted a few hundred feet in front of the tracks and tells you to look, listen and slow down, because you may have to stop. Roll down the car window and listen carefully, for if the wind is blowing in the wrong direction, you may not hear the train. Don't try to figure time and distance. You'll never have another chance if you figure incorrectly. Passing is prohibited at a railroad crossing.