1899, Thomas Francis Woodlock, "Ton-mile Cost." Booklet. Reprinted From the Wall Street Journal and Published By Dow, Jones & Co.[1], Dow, Jones & Co., page 4:
In the short series of chapters which is here begun, an attempt will be made to set down and illustrate some of the main principles governing the transportation of freight by railroads in the United States. The primary object is to convey a clear idea of what is meant by the "Ton-mile," the "Train-mile," the "Unit of service," the "Unit of product," and the various other words and phrases commonly used to designate the main facts and things in the Railroad industry.
1912 July, George D. Mumford, “A Study in Railroad Efficiency: The Virginan Railway”, in Moody's Magazine[2], volume 14, number 1, page 40:
The Virginian Railway in the year 1911, while still hampered by insufficient equipment, hauled over 2,700,000 tons of freight at a cost of 2.1 mills per ton-mile. Its average rate per ton-mile was 3.6 mills, or less than one-half of the average ton-mile rate in 1910 in the United States. And with a rate of 3.6 mills, the Virginian made a net profit 1.5 mills per ton-mile. Its operating ratio was 59 per cent and its per centage of net earnings to gross 41 per cent. / The ton-mile cost is a much truer basis for comparison of operating efficiency than the mere operating ratios themselves. Railroads "A" and "B" may both have an operating ratio of 60 per cent, but Railroad "A" may have attained this operating ratio on the average ton-mile rate of 4 mills while Railroad "B" may have attained the same ratio on a ton-mile rate of 8 mills.
1963 September, “French Railways' quarter-century of expansion”, in Modern Railways, page 189:
Nevertheless, since 1938 the French National Railways' passenger traffic has risen by 60 per cent and freight traffic, in terms of ton-miles, 130 per cent.
