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Depreciation

The distribution by cost items shown in the bottom portion of table 3 was essential to computing depreciation. For purposes of this computation, the depreciation rates previously listed in this report were to be applied to these cost items in accordance with their age on June 30, 1957. A summary of these costs by age groups is shown in table 4.

The relatively large amounts in the zero age group are due to the inclusion, in this study, of costs for work which was under construction or awarded to contract on June 30, 1957. (Work financed under the 90-10 Federal-aid provisions of the 1956 act is not included.)

The computed depreciation on the amounts in table 3 was $174 million, of which $74 million was on toll roads and $100 million on free roads. No attempt was made in this study to investigate bond-financed projects for purposes of comparing the amounts of this depreciation with the amounts of bonds called or sinking fund accruals for bond redemption.

In table 5 are listed the amounts of cost new less depreciation for the same distributions as shown for the cost-new amounts in table 3.