Which of the following is a potential hazard when operating cranes?

Poorly maintained equipment presents a significant hazard when operating cranes due to the increased risk of mechanical failure and accidents. Regular maintenance is essential in ensuring that all parts of the crane are functioning properly and safely. If equipment is not maintained, it can lead to issues such as brake failure, cable breakage, or problems with the hoisting mechanisms, which can compromise the safety of the operator and ground personnel.

In contrast, low operating costs, clearly marked lifting zones, and regular inspection of lifting equipment are generally viewed as positive aspects of crane operation. Low operating costs might indicate efficiency, while clearly marked lifting zones help to ensure safety by guiding operators and personnel. Regular inspections are crucial as they help identify any potential issues before they lead to hazards, making them an essential part of safe crane operations. Thus, only poorly maintained equipment stands out as a clear potential hazard.