What is the proper way to signal a crane operator to "stop" when not within sight?

To effectively signal a crane operator to "stop" when not within sight, using radio communication or alert methods is the most appropriate approach. This method ensures clear, direct, and reliable communication between the ground personnel and the crane operator, minimizing the risk of accidents or misunderstandings.

When working at a site where visual contact is not possible, relying on visual signals would not be practical since the operator cannot see the signals being given. Waving arms frantically may create confusion rather than provide a clear instruction and is not a reliable method of communication over distances. Shouting loudly also falls short, as sound may not carry well enough to get the operator's attention or could be drowned out by surrounding noise.

Therefore, utilizing radio communication allows for immediate and effective instructions, ensuring that the crane operator receives the "stop" signal clearly and can act accordingly to maintain safety on the job site.