The self-propelled Rail Diesel Car was introduced in 1949 as a low-cost alternative for branchline and commuter runs, available in five combinations of coach seating and baggage and mail space. Power came from two diesel engines and a mechanical drive, and unlike earlier gas-electric "Doodlebugs," multiple RDCs could be coupled and controlled from one cab. Chicago and North Western bought three RDCs, numbered 9933 through 9935, to evaluate for local and commuter service, but by 1957 chose diesel-hauled bi-level commuter trains and traded all three to the Chesapeake and Ohio. Car 9933 then operated on the Chesapeake and Ohio as 9061 and on its affiliate Baltimore and Ohio as 1971 until 1984, when the Massachusetts Bay Transportation Authority bought it. It remained in Boston-area commuter service as MBTA 10 until its retirement and acquisition by IRM. Built by Budd Co., it had 550 horsepower from two GM 6-280 prime movers, weighed 113,120 pounds, rode on four axles, and carried 80 passengers.