The self-propelled railcar was not a new concept in North American railroading. Beginning in the 1880s railroads experimented with steam-powered railcars on branch lines, where the costs of operating a conventional steam locomotive-hauled set of cars was prohibitive. These cars failed for several reasons: the boiler and engine were too heavy, water and fuel took up too much space, and high maintenance costs eliminated whatever advantage was gained from reducing labor costs. In the 1900s steam railcars gave way to gasoline, led by the McKeen Motor Car Company, which produced 152 between 1905–1917. J. G. Brill sold over 300 "railbuses" in the 1920s. Newcomer Electro-Motive Corporation, working with the Winton Motor Carriage Company, dominated the market at the end of the 1920s but had exited it completely by 1932 as the Great Depression gutted rail traffic.
The Budd Company entered the market in 1932, just as EMC exited. Heretofore Budd was primarily an automotive parts subcontractor but had pioneered working with stainless steel, including the technique of shot welding to join pieces of stainless steel. This permitted the construction of cars which were both lighter and stronger. Budd partnered with Michelin to construct several rubber-tyred stainless steel rail cars powered by gasoline and Diesel engines. These saw service with the Reading Company, Pennsylvania Railroad, and Texas and Pacific Railway. The cars were underpowered, the tires proved prone to blowouts and derailments, and the cars were unsuccessful.
Budd revived its railcar concept after Diesel engines with a suitable combination of power and weight became available in 1938, albeit with more conventional steel wheels. In 1941 Budd built the Prospector for the Denver and Rio Grande Western Railroad. This was a two-car diesel multiple unit. Each car had a pair of 192 horsepower (143 kW) diesel engines and was capable of independent operation. The cars were constructed of stainless steel and included a mix of coach and sleeping accommodations. The design was popular with the public but undone by the difficult operating conditions on the D&RGW. It was withdrawn in July 1942, apparently another failure. However, several technical advances during the Second World War encouraged Budd to try again.
The war years saw improvements in the lightweight Detroit Diesel engines and, just as importantly, the hydraulic torque converter. Budd, which by then had produced more than 2,500 streamlined cars for various railroads, took a coach design and added a pair of 275 hp (205 kW) 6-cylinder Detroit Diesel Series 110 engines. Each drove an axle through a hydraulic torque converter derived from the M46 Patton tank. Budd broke with the "railbus" designs of the 1920s–1930s and used a standard 85-foot (26 m) passenger car shell. The cars could operate singly, or in multiple. The result was the RDC-1, which made its public debut at Chicago's Union Station on September 19, 1949.
Budd manufactured five basic variants of the RDC:The RDC-1: an 85 ft (25.91 m) all-passenger coach seating 90 passengers. It weighed 118,300 pounds (53,700 kg) empty.
The RDC-2: an 85 ft (25.91 m) baggage and passenger coach configuration (combine) seating 70 passengers. The baggage area was 17 ft (5.18 m) long. It weighed 114,200 pounds (51,800 kg) empty.
The RDC-3: an 85 ft (25.91 m) variant with a Railway Post Office, a baggage compartment and 48 passenger seats. It weighed 117,900 pounds (53,500 kg) empty.
The RDC-4: a 73 ft 10 in (22.50 m) variant with only the Railway Post Office and baggage area. It weighed 109,200 pounds (49,500 kg) empty.
The RDC-9: an 85 ft (25.91 m) passenger trailer seating 94, a single 300 horsepower (220 kW) 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 300 horsepower (220 kW) instead of 275 horsepower (205 kW). 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.
In an experiment toward high-speed rail, the New York Central (NYC) fitted a pair of 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 184 mph (296 km/h) between Butler, Indiana, and Stryker, Ohio. It was never intended that jet engines propel regular trains. With the news about high-speed trains overseas, particularly the Japanese Shinkansen bullet trains, American railroads were under pressure to catch up. By strapping a pair of military surplus jet engines onto a Budd car, NYC found an inexpensive way to conduct research into how conventional rail technology behaves at very high speeds.
In 1956, the New York, New Haven and Hartford Railroad ordered a custom-built, six-car train set based on the RDC design named the Roger Williams. It consisted of two single-ended cab units and four intermediate cars to make a complete train. The units were fitted with third-rail shoes, electric traction motors, and associated gear for operation into Grand Central Terminal, though this was short-lived. In the New Haven's later years, the set was broken up, and used with regular New Haven RDCs, and by Amtrak into the 1980s.
In 1961, five cars were built under license in Australia by Commonwealth Engineering for the New South Wales Government Railways. They were smaller than the standard RDC in all dimensions due to a narrower loading gauge. One car was built with a buffet/snack bar accommodation in one end and was unique in being non-powered. They operated the South Coast Daylight Express between Sydney and Bomaderry. They were converted to locomotive hauled carriages in 1982 and withdrawn in 1993.
In the late 1970s Budd sought to replace the aging RDCs with a new design, the SPV-2000. The body shell was based on an Amfleet coach, not the RDC. Like the RDC it was 85 feet (26 m) long, stainless steel, and powered by twin diesel engines. The design was beset with mechanical problems and Budd sold only 30 cars.
The vast majority of RDCs were owned and operated by railroads in the United States. They could be found on branch lines, short-haul intercity routes, commuter routes, and even long-distance trains. The Western Pacific Railroad used a pair of RDC-2s to operate the Zephyrette, a supplement to the California Zephyr. The two cars ran between Oakland, California and Salt Lake City, Utah, 924 miles (1,487 km), three days a week. Examples of shorter intercity services were the Chicago, Rock Island and Pacific Railroad's Choctaw Rocket and the Baltimore and Ohio Railroad's Daylight Speedliner. The latter ran between Pittsburgh and Philadelphia and included full dining service. A notable example of the RDC's flexibility occurred on the Pennsylvania-Reading Seashore Lines, where a single train would depart Camden, New Jersey and split into multiple trains to serve different destinations on the Atlantic coast.
The largest RDC fleets were in the Northeast United States. The New York, New Haven and Hartford Railroad (New Haven) acquired 40 RDCs, which it called "Shoreliners", in 1952–53. By 1955 these accounted for 65% of the New Haven's passenger routes. This achievement was eclipsed by the Boston and Maine Railroad, whose fleet grew to 108 by 1958. The B&M's RDCs operated 90% of the company's passenger routes, including its extensive commuter operations around Boston, Massachusetts.
The results in commuter service outside the B&M were mixed. Budd had not designed the RDC for commuter service and discouraged operators from using it to haul coaches. The Long Island Rail Road and Chicago and North Western Railway, which had extensive networks in Long Island and Chicago, respectively, evaluated the RDC but made few orders. Conversely, the Reading Company's 12 RDC-1s lasted on the Philadelphia–Reading and Philadelphia–Bethlehem routes well into the SEPTA era.
For several railroads the RDCs, because of their low overall cost and operational flexibility, were the last passenger trains in operation. Examples include the Duluth, Missabe, and Iron Range Railway, the Duluth, South Shore and Atlantic Railway, the Lehigh Valley Railroad, and the Northwestern Pacific Railroad, where RDC service survived until the formation of Amtrak in 1971.
Many RDCs remained in service throughout the 1970s and 1980s. Amtrak acquired 24 (including three from the Roger Williams), mostly for use in Connecticut. The Massachusetts Bay Transportation Authority (MBTA) acquired the B&M's fleet and continued operating them until 1985. The Alaska Railroad acquired five RDCs, three from SEPTA and two from Amtrak between 1984–1986. These were all sold or out of service by 2009. Portland, Oregon's TriMet acquired two of these for use on its Westside Express Service. Trinity Railway Express acquired thirteen RDCs from Via Rail in 1993 for use on commuter service between Dallas and Fort Worth, Texas. The Denton County Transportation Authority leased several for A-train service pending the arrival of new Stadler GTW 2/6s diesel multiple units.
Both the Canadian National Railway (CN) and Canadian Pacific Railway (CP) purchased RDCs. The Canadian National purchased 25 cars outright, and acquired many more second-hand from the Boston and Maine Railroad. These cars, which CN called Railiners, were used primarily on secondary passenger routes. CP purchased 53 cars. The first one ran on November 9, 1954, between Detroit and Toronto. It was the first stainless-steel passenger train to operate in Canada. CP used the RDCs, which it called Dayliners, throughout its system. CP also made extensive use of them on commuter trains around Montreal and Toronto. Via Rail inherited many of these cars when it took over CN and CP passenger services in 1978. Via continues to use RDCs on the Sudbury–White River train in Ontario.
Another Canadian purchaser of RDCs was the Pacific Great Eastern Railway, which operated passenger service between North Vancouver and Prince George. RDCs continued to operate on this route until all passenger service ended under BC Rail, PGE's successor, in 2002.
Refurbished RDCs were considered for Blue22, a rail service between Toronto Union Station and Pearson Airport, by 2010. The service, which was transferred to Metrolinx ownership and opened in 2015 as the Union Pearson Express, ultimately used new Nippon Sharyo DMU trains instead.
Three RDC-1s, collectively designated the CB class, were exported to Australia in 1951 to operate for the Commonwealth Railways. These cars were transported to Australia by Budd engineer Joseph F. Grosser. They ran between Port Pirie, Woomera Tarcoola, Marree and Whyalla before being transferred to Australian National in July 1975 and withdrawn. In 1986 they were reinstated on the Iron Triangle Limited from Adelaide to Whyalla and the Silver City Limited from Broken Hill before being withdrawn in December 1990.
In February 1988, CB3 was damaged in an accident and not repaired while the other two were withdrawn in December 1990 and placed in store at Port Pirie. CB1 was donated to the National Railway Museum, Port Adelaide in August 1996 while the other two were included in the sale of Australian National to Australian Southern Railroad in August 1997 being sold to Bluebird Engineering in 1999.
RFFSA (Brazilian Federal Railways) purchased four RDC-1s and two RDC-2s in 1958. These were 1,600 mm (5 ft 3 in) but otherwise standard configuration. RFFSA ordered 23 more cars in 1962–1963. Four of these were 1,600 mm (5 ft 3 in) RDC-1s. The other 19 were 1,000 mm (3 ft 3 3⁄8 in) and varied considerably from the standard RDC-1 design. The car body was based on the Pioneer III coach. Internal seating was 48 with a small buffet area or 56 in an all-coach configuration. Several RDCs remain active on the Serra Verde Express tourist train.
In the 1950s both major railway companies in Cuba purchased RDCs. Consolidated Railways of Cuba (Ferrocarriles Consolidados de Cuba) ordered 11 RDC-1s and 5 RDC-2s in 1950. These operated either singly or in multiple units of up to three cars. The Western Railways of Cuba (Ferrocarriles Occidentales de Cuba) ordered four RDC-1s and six RDC-3s in 1956–57. The cars remained in use after the Cuban Revolution with the Ferrocarriles de Cuba and operated into the 1980s.
The Arabian American Oil Company constructed a standard gauge railway in cooperation with the Saudi government. The company ordered three RDC-2s in 1951, supplemented by a fourth in 1958. The cars operated on various routes originating in Dammam. All were converted to unpowered trailers by 1965.
Budd constructed 398 RDCs between 1949 and 1962. The table below does not include the six cars which comprised the Roger Williams, nor derivative designs built under license.
Numerous RDCs have been preserved on tourist lines and in museums. Holders include: