The Budd Rail Diesel Car, mostly only called RDC, was an early diesel railcar that had been developed for rural lines with a low passenger density and for flexible commuter service. Like in other countries, it was built to be operated cheaper than short loco-hauled trains. Each car had two cabs and could run by itself, but multiple cars could be combined and operated by a single person.

Budd took a standard 85-foot coach and mounted two six-cylinder diesel engines in it. These were of the Detroit Diesel 110 family and developed 275 hp each. Each engine transmitted its power via a hydraulic gearbox onto the inner axle of each truck. There was also the RDC-9 trailer variant that had no cabs and only one engine delivering 300 hp. 

Most RDC were used in the north eastern US, but there were also other operators in North America, as well as in South America, Asia and Australia. In the US, most were retired in the eighties. In other countries their career was longer. For example, the Canadian Via still uses them today.