For years attempts have been unsuccessfully made by accountants to effect the primary separation between expenses of passenger and freight business,[46] in order to determine the cost of transportation per unit in each case. Some companies like the Louisville & Nashville and the Burlington system, still divide up the two, usually on the basis of the engine mileage for each class of traffic. This may be serviceable enough for comparisons of costs from year to year in the same company, but it has no general value and it may, moreover, become highly misleading. The most absurd conclusions may result. Thus at one time it appeared from such data, compiled by the Interstate Commerce Commission, that the New York Central, with five times the density of traffic of the Illinois Central, was actually conducting its freight business at a much higher cost per ton mile. Such inconsistencies induced the Interstate Commerce Commission in 1894 to abandon the attempt at any such primary separation of accounts.[47] It has since been reattempted, in special cases, as by the Wisconsin Railroad Commission in its notable "Two-cent Fare" decision in 1907, the division being made according to a number of different criteria.[48] But it is plain that a very large proportion--probably over half--of the expenditures for freight and passenger business are entirely joint, however distinct the revenues from each service may be. We have seen that approximately two-thirds of the outgo is incurred on behalf of the property as a whole. Certain expenses, to be sure, such as train wages, coal consumption and the maintenance of rolling stock, are readily divisible; but with respect to the maintenance of way and structures--about forty per cent. of the total outgo--all guides fail. Even in respect of the cost of rails, due to wear and tear of train movement, we are quite at sea in the allocation of expenses. Freight trains may indeed be four times as heavy as passenger trains; but, on the other hand, they move at far slower speeds. And then, finally, how about the large item of capital cost, the proportion of outgo for fixed charges? This equals about twenty-seven per cent. of the total expenditures for the United States as a whole. We may, of course, divide these expenses arbitrarily on the basis of the relative gross revenue from freight and passenger business respectively. And yet how absurd it would be to attempt to allocate an expense of a million dollars for the abolition of grade crossings in this way. As between the New Haven road, with passenger and freight revenues about equal, and a western road with only one-tenth of its income derived from passengers, the apparent cost of freight business on the eastern road would be absurdly reduced by any such process. The facts are plain. So many expenditures are incurred indiscriminately on behalf of the service as a whole--being an indispensable condition for operation