Railroads. Freight and passenger train service unit costs (selected expense accounts) of class 1 steam roads in United States, including proportion of mixed-train and special-train service (compiled from 164 reports representing 180 steam roads, switching and terminal companies not included), Mar. 1922 and 1921, and 3 months [ended with Mar.] 1922 and 1921; [prepared in] Bureau of Statistics.