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.
Multi-axle bus
Tri-axle double-decker buses are common in high capacity operating environments where articulated buses are not used, such as Hong Kong and Singapore. Tri-axle buses also see high volume use in Dublin, Ireland. Imported tri-axle buses were used initially by Megabus for high capacity low cost intercity travel in the UK.