The manner in which heavy capital outlay for maintenance accompanies as well as partly accounts for a decline in the cost of conducting transportation on American roads, is graphically shown by the diagram on the next page.[41] During ten years a steady decline in direct operating costs has accompanied an equally marked upward tendency in expense of maintenance. The bearing of this on the problem of rate advances in future is direct. Profitableness results from two separate sources; economical operation such as longer trains and better loading, and also from far heavier capital investment in plant, by which such operation is rendered possible.[42] Both alike, however, attend upon increased volume of business. Heavy capital investment may lessen immediate maintenance charges,--lower grades and straighter alignment naturally wearing less; but, on the other hand, the burden of interest and other fixed expenses steadily grows. How will they stand toward one another by 1925 on the eastern trunk lines? Will growth of business bring lower rates or not? A fine field for further analysis is as yet unworked. [Illustration: _RATIO OF MAINTENANCE OF PROPERTY AND CONDUCTING TRANSPORTATION TO TOTAL OPERATING EXPENSE._] One final relation between operating and fixed expenses is left for consideration. It is so well put by J. Shirley Eaton in an unpublished paper, that it can best be stated in his own words: "It is impossible to have an absolute and universal line of demarcation between the direct and the fixed expense, that shall be the same on all roads. One road chooses to reduce a grade and thereby increase the capital account in order to save in the current expense of a helper at a hill or the lost margin of efficiency of the loaded train on the level. The relation between a current expense and the annual charge of the capitalized cost on a fixed plant that performed the same service, was well illustrated in a case arbitrated by Mr. Blanchard in New Orleans. One road which did not have access to the heart of the city undertook to compensate its disadvantage by trucking to and from its depot. The hire of a public truckman to perform the service for its patrons was very soon commuted to the practice of paying the amount of the truck expense to the consignee by deducting it from the freight bill rendered, the consignee or shipper performing the service. This, known as 'drayage equalization,' was claimed by competitors to be in the nature of a rebate to secure business. The arbitrator decided that the first roads had elected to buy their right of way into the heart of the city; and the road that had not built into the city elected to pay the expense of the same service in the shape of a current drayage bill instead of in the shape of interest on money invested in right of way. Therefore he decided there was no cause for complaint."[43]