What does the hand signal for 'stop' look like?

The hand signal for 'stop' is indicated by swinging the arm horizontally at a right angle to the track. This gesture effectively communicates to train operators and personnel that immediate stopping is required. The horizontal position clearly distinguishes the signal from other directions of motion, making it easily recognizable from a distance.

The other options, while involving arm movement, do not conform to the standard hand signal for stopping. For instance, a vertical motion may be associated with different signals that indicate other actions rather than a halt. Similarly, circular movements or motions above the head are less universally recognized for the specific command to stop. Understanding the correct signals is crucial for maintaining safety and communication on the tracks.