Tank Car Mileage Equalization is a process between carriers and private car owners supervised by the STB in accordance with tariff RIC 6007.

Tank car mileage is reported through the Car Hire Data Exchange Process (CHDX) for the year. Annually, loaded and empty mileage is compared. For each car initial, empty mileage can exceed loaded mileage by up to six percent (6%) without triggering a charge. If the empty mileage for a mark exceeds the loaded mileage by more than six percent, Railinc invoices the mark owner at a rate calculated annually per the RIC 6007 tariff.

A copy of the RIC 6007 tariff is available for download here:
https://public.railinc.com/resources/national-tariffs