Double-decker bus
With the exception of coaches, double-decker buses are uncommon in the United States. Many private operators, such as Megabus, run by Coach USA, employs double-decker buses on its busier intercity routes.
Rigid bus
Rigid buses may be of either single-deck or double-deck design, and may have either two axles or multi-axles. However, the expression "rigid bus" is seldom used to describe a double-decker bus, because very few double-decker buses have anything other than a rigid chassis.