Depreciation
Depreciation (of depreciable property and equipment). The loss in service value, not restored by current maintenance, incurred in the course of service from causes known to be in current operation, against which the carrier is not protected by insurance, and the effect of which can be forecast with reasonable accuracy. The causes of depreciation include wear and tear, decay, action of the elements, inadequacy, obsolescence, changes in the art, changes in demand, and requirements of public authorities.