Code of Federal Regulations Title 49. Transportation 49 CFR § 1201.4-3 4–3 [1201.4–3] Depreciation records to be kept

(a) The carrier shall maintain for each class of property in convenient and accessible form engineering and other data bearing on prospective service lives.

(b) The carrier also shall keep such records of depreciable property and property retirements as will reflect the service life of each class of property which has been retired, or will permit the determination of service life indications by past experience of useful life tenure of comparable property, turnover, or other appropriate methods;  also such records as will reflect the percentage of value of the salvage for property retired from each class of depreciable property.

(c) For purposes of analysis the carrier shall maintain subsidiary records in which the accumulated depreciation account is broken down into component parts corresponding to each primary account to show the current credits and debits and the balance for each account. Such detailed information shall be reported annually to this Board. For balance sheet purposes, the accumulated depreciation account shall be treated as a single composite account for depreciable property.

(d) Carriers shall be prepared to justify all track depreciation rates by keeping appropriate data on the service lives and salvage values of track components which went into the life and net salvage computation of each primary account in each density category.

(e) The investment and related accumulated depreciation for accounts 3, 4, 5, 8, 9, 11 and 39 must be maintained by distinct traffic density categories. Each line segment shall be identified on January 1 of each year as belonging to one of the following traffic density classes, based on the average traffic density in the preceding three years: