What is an essential pre-lift safety measure when working near power lines?

An essential pre-lift safety measure when working near power lines is to ensure all personnel are clear. This practice is crucial because the proximity of power lines poses a significant risk of electrical hazards. When operating a mobile crane or digger near these lines, it's vital to establish a safe zone that keeps all personnel at a safe distance to prevent accidental contact with live wires, which can lead to severe injuries or fatalities.

Maintaining clear areas around power lines protects workers from potential electric shocks and ensures that everyone maintains focus on the crane operations without unnecessary distractions or risks. This precaution helps in minimizing the chance of accidents and promoting a safe work environment.

In contrast, the other options may not directly address the specific dangers posed by power lines. Using longer cables or increasing the height of the crane does not mitigate the risk of electrocution if personnel are still within a hazardous area. Wearing safety gear is always recommended but is not sufficient on its own if individuals are in potential danger from electrical sources. Therefore, ensuring all personnel are clear is the most critical safety measure in this scenario.