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 163 reports representing 179 steam roads, switching and terminal companies not included), Sept. 1922 and 1921, and 9 months [ended with Sept.] 1922 and 1921; [prepared in] Bureau of Statistics.