I've posted to files section the percentage of home road cars on-line from 1940 to1960. This information is from Car Service Division records. Thought it might be interesting with the current discussion of B&A hoppers.
Service Order C411 was issued Sept 23, 1924 requiring the return of cars of C&O, L&N, VGN and N&W ownerships to home line in empty movement. This order was cancelled and reinstated many times between 1924 and October 1938 and was then maintained continuously.
Service Order C421 was issued June 4, 1947 forbidding the loading of empty Clinchfield and Interstate coal cars by other railroads in the Pocahontas and Southern Districts.
Service Order C431 was issued June 20, 1947 prohibiting use of empty C&EI, CB&Q, IC and MP coal cars in the US or Canada east of NM, CO, WY, MT and Alberta or west of a line from Sandusky, OH through Marion, Columbus and Portsmouth, OH to Huntington, WV. Cars of this ownership located in this territory had to be returned home empty to owner.
Service Order C451 was issued Dec 12, 1949 to 15 Western railroads to discontinue loading of D&RGW and D&SL coal cars and return home direct or via service route.
Service Order C461 was issued June 25, 1950 to railroads East of Chicago and St. Louis and north of Ohio-Potomac rivers, also in Canada east of Winnipeg that all B&O hoppers be sent home.
Service Order C471 was issued Oct 9, 1950 to 12 turnk lines and 2 St.Louis terminal switch lines requiring SLSF hoppers to be sent home.