Final answer:
A commercial vehicle will be placed out of service if there is even one broken or missing leaf in the leaf spring assembly, to ensure the safety and stability of the vehicle.
Step-by-step explanation:
When inspecting a commercial vehicle's leaf spring assembly in the suspension system, if at any point there is one broken or missing leaf, that vehicle will be placed out of service. This standard ensures the safety of the vehicle as well as other road users. The integrity of the leaf springs is crucial for maintaining control and stability of the vehicle.