weighed empty. The RDC-9: an passenger trailer seating 94, a single engine and no control cab. Several railroads used the designation "RDC-5": the Canadian Pacific Railway for RDC-2s converted to full-coach configuration and the Canadian National Railway for RDC-9s it purchased from the Boston and Maine Railroad. In 1956, Budd introduced a new version of the RDC, with several improvements. The new cars had more powerful versions of the Detroit Diesel 6-110 engines, each of which produced instead of . They also featured higher-capacity air conditioning and more comfortable seating. The appearance changed slightly as well: the side fluting continued around to the front of the car and the front-facing windows were smaller. Jet propulsion In an experiment toward high-speed rail, the New York Central Railroad fitted a pair of General Electric J47 jet engines from a Convair B-36, complete in their twinned nacelle from the bomber's engine installation, atop one of their RDCs and added a shovel nose front (much like a later automotive air dam) to its cab, but extended upwards, covering the entire front end. This RDC, which NYC had numbered M497, set the United States speed record in 1966 when it traveled at just short of between Butler, Indiana, and Stryker, Ohio. It was never intended that jet engines propel regular trains. With high-speed trains advancing overseas, particularly the Japanese Shinkansen bullet trains, American railroads were under pressure from the federal government to catch up. The test runs and subsequent American rail speed record set on July 23, 1966, provided valuable data on the interaction between flanged wheels and rail at high speeds, as well as stress on wheel bearings and track infrastructure. At the same time the test took place, the Central announced plans to discontinue most of its long-distance trains, including the renowned 20th Century Limited. Trains editor David P. Morgan observed that "...[the New York] Central will never quite convince anyone that the RDC's jet exploit was more a scientific feat than a calculated circus to take the curse off the Centurys funeral notice." Historian Chuck Crouse expressed skepticism in 1990 about the test's usefulness: "What, if anything, did the tests prove is anyone's guess." Derivatives In 1956, the New York, New Haven and Hartford Railroad ordered a custom-built, six-car train set they named the Roger Williams, based on the RDC design. It consisted of two single-ended cab units and four intermediate cars