What safety measure should be taken before operating heavy machinery?

Conducting a pre-operation inspection is a critical safety measure that ensures the machinery is in proper working condition before operation. This inspection typically includes checking various components such as brakes, lights, hydraulics, and safety devices to confirm they are functioning properly. By performing this inspection, operators can identify any potential issues that could lead to equipment failure or accidents, thereby protecting the safety of personnel and the integrity of the worksite.

The other options, while they may touch on aspects of machinery operation, do not encompass the comprehensive approach of a pre-operation inspection. Checking fluid levels is just one part of the maintenance necessary and cannot ensure overall safety. Training staff on load limits is important, but it does not address the immediate condition of the equipment being used. Verifying fuel prices is not related to safety and does not impact the operation of the machine itself. Thus, conducting a pre-operation inspection stands out as the most effective measure for ensuring safety before operating heavy machinery.