The total cost of motive power by the use of locomotives must be determined by a consideration of the first cost of the locomotive, the cost of maintaining it in condition for work, and the cost of operating it. Considering the variable life of locomotives of different cost, we must consider, instead of the first cost of the locomotive, the average annual cost which will be the equivalent of the actual total cost through the period of the life of the locomotive. In general it may be said that the heavier and more expensive locomotives have been found most economical, considering the ton-miles of hauling which they accomplish during their total life, than the fighter and less expensive locomotives, but the economics of any type of locomotive can only be determined by a consideration of all the terms involved. As a general statement we may say that a locomotive is the cheapest which will haul a ton-mile over any combination of grades and curves at a less total cost (considering all items) than will be charged to any other engine of its class. Strictly speaking, even the above test should be applied only to compare the locomotives of one class, and perhaps only to freight-locomotives. Passenger-locomotives usually have the requirement of high speed, which cannot be obtained except at a proportionate sacrifice in hauling capacity. But it is not even possible to consider that the test of any one locomotive will be an accurate measure of the efficiency of that type, since it is often found that locomotives, which are built at the same shop, according to identical plans and used in the same kind of service, will have a very different history regarding shop repairs, fuel and supplies consumed, etc. Of course there is a reason for this in each case, and the blame is ordinarily laid on the enginemen. While this is frequently justifiable the engine-builder may also be somewhat to blame. A summation of the percentages of Items 25 to 27 and 80 to 85 in the classification of operating expenses, referred to in Chapter VI, shows that the average for the years 1908, 1909 and 1910 is as follows:
Percentage of total cost of a train-mile.
Cost in cents per train-mile.
Items 25-27. Repairs, renewals, and depreciation of road locomotives .................
Item 80. Road enginemen, wages...........
" 81. Enginehouse expenses, road........
" 82. Fuel for road locomotives..........
" 83. Water for road locomotives........
" 84. Lubricants for road locomotives.....
" 85. Other supplies for road locomotives .
The average cost per train-mile for the same three years equals 146.525 c. If we multiply these percentages by this average cost we obtain the average cost in cents per train-mile for these various items, as given in the last column of Table X.