(a) Where the carrier maintains records of the repairs by individual locomotive units or classes of locomotive units:

(1) If individual locomotive units or classes of locomotive units are used exclusively in road-freight, road-passenger, yard-freight, or yard-passenger service, the separation shall be actual.

(2) If individual locomotive units or classes or locomotive units are used interchangeably (common) in road-freight (including train-switching), road passenger (including train switching), yard-freight or yard-passenger service, separate the heavy shop repairs between these services on the basis of run-out unit miles of individual locomotive units or classes of locomotive units since the previous shopping; and separate the cost of running repairs between such services on the basis of the miles run by the individual locomotive unit or class of locomotive unit in each service during the accounting period for which the separation is being made.

(b) Where the carrier maintains records of heavy shop repair costs by individual locomotive units or classes of locomotive units, but does not maintain records of the cost of running repairs by individual locomotive units:

(1) The heavy shop repairs shall be separated as indicated in paragraph (a) of this section.

(2) The common expenses of running repairs shall be separated among road-freight (including train switching), road-passenger (including train switching), yard-freight and yard-passenger services on the basis of locomotive unit miles or locomotive ton-miles for the accounting period for which the separation is being made.

(c) Where the carrier does not maintain records of either heavy shop repairs or running repairs by individual locomotive units or classes of locomotive units: The expenses shall be separated among road-freight service (including train-switching), road-passenger service (including train switching), yard freight, and yard-passenger services, on the basis of locomotive unit-miles or locomotive ton-miles for the accounting period for which the separation is being made.