When must an operator test the crane's brakes?

The correct response highlights the importance of safety and operational readiness when handling heavy loads. An operator must test the crane's brakes each time a load that is 90% or more of the maximum line capacity is handled. This requirement ensures that the operator is aware of the crane's braking performance under significant load conditions, which is critical for preventing accidents and ensuring safe lifting operations.

Testing the brakes before handling substantial loads helps to confirm that they function correctly under the stresses that will be encountered during operation. This practice is aligned with safety precautions to minimize the risk of brake failure, which can have severe consequences when dealing with heavy equipment.

While it's also vital to conduct regular maintenance and checks as part of an overall safety program, the requirement to specifically test the brakes before handling such substantial loads emphasizes the operator's responsibility for immediate safety in high-risk situations.