Which of the following is a crucial safety measure during stacker operation in congested areas?

During stacker operation in congested areas, warning workers of the approach is an essential safety measure. This practice helps to mitigate potential accidents and injuries by ensuring that workers are aware of the stacker’s location and movements. Congested environments are often crowded with personnel and obstacles, making it challenging for operators to maintain visual awareness of everything happening around them. By signaling or using audible warnings, operators can alert those nearby to the stacker's presence, allowing workers to stay clear of its path.

The other choices do not address the specific risks associated with operating a stacker in confined spaces. Driving without a load reduces some risk but doesn't solve the problem of spatial awareness among operational and pedestrian personnel. Using high beams at night might improve visibility for the operator, but it does not directly alert others in the area. Driving with doors open might seem convenient for the operator but creates additional safety hazards and is generally unsafe, as it increases the risk of falls or accidents, further endangering both the operator and nearby workers.