When should brakes be coupled while operating machinery?

Brakes should be coupled while operating machinery primarily for safety and control. Coupling the brakes allows the operator to maintain better control over the machinery, particularly while driving on public roads where regulations require equipment to be operated in a safe manner. On public roads, the machine is subject to traffic laws, and coupled brakes help prevent the vehicle from rolling or becoming unstable.

During activities like loading, it is essential to ensure the machine remains stable, but coupling the brakes in that context isn't the primary focus as it would be while driving. Parking is another scenario where brakes are typically engaged to secure the machine; however, the context of the question focuses on operation rather than merely stopping. When driving on private property, while safety is still crucial, the strict requirements enacting the use of coupled brakes do not apply as rigorously as they do on public roads; hence, the focus on correct operation aligns more closely with option A.