1953, United States. Dept. of Agriculture. Production and Marketing Administration,A study of conditions affecting the transportation of grain by railroad:
From 1940 to 1946,carloadings of grains ranged from about 28 to 35 percent of total shipments of products of agriculture.
1960 November, David Morgan, “"Piggyback"—U.S. success story”, inTrains Illustrated, page683:
In 1955, for example, 32 railroads reported 168,150 piggybackcarloadings; in 1959 50 roads loaded 415,156 cars; [...]. T.O.F.C. still accounts for little more than 2 per cent of all U.S.carloadings but industry experts expect that percentage to reach between 25 and 50 per cent within the foreseeable future.
