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.
Hybrid electric bus
In the United Kingdom, Wrightbus has introduced a development of the London "Double-Decker", a new interpretation of the traditional red buses that are a feature of the extreme traffic density in London. The Wright Pulsar Gemini HEV bus uses a small Diesel engine with electric storage through a lithium ion battery pack. The use of a 1.9-litre Diesel instead of the typical 7.0-litre engine in a traditional bus demonstrates the possible advantages of serial hybrids in extremely traffic-dense environments. Based on a London test cycle, a reduction in CO emissions of 31% and fuel savings in the range of 40% have been demonstrated, compared with an "Euro-4" compliant bus.