This nickname refers to a self-propelled, single-car passenger unit designed to run independently on branch lines or low-density routes. Unlike standard commuter trains that require multiple coupled cars, these standalone units contain both the motive power and passenger seating in one chassis. Crews often use the term because of their rounded, self-contained appearance and their tendency to bounce on lighter trackage.
Dispatch wants us to take the bubble car down the valley spur to cover the afternoon commuter run.
While classic Budd RDCs are the most famous North American examples, the nickname applies to any standalone passenger unit bouncing down a rural spur.
Also heard as
- RDC
- Budd car
Related terms
Railcar
A self-propelled railway vehicle designed to carry passengers.
Multiple unit
A train configuration where several self-propelled cars are coupled and controlled from a single cab.
Branch line
A secondary railway line that diverges from a main route.
Diesel multiple unit
A train consisting of self-propelled passenger cars powered by onboard diesel engines.