Double-decker bus
The first commercial horse-drawn double-decker omnibuses were introduced in England in 1847 by Adams & Co. of Fairfield, Bow, then improved upon by John Greenwood, who introduced a new double-decker in 1852.
Alexander Dennis Enviro500
Dennis also built one 12-metre Enviro500 demonstrator for long-term loan. It was first loaned to Community Transit between 2007 and 2009 which put it into service on 1 August 2007, the bus was used on commuter routes between Seattle and various points in Snohomish County during its first year in operation. From September 2010, it was loaned to Strathcona County Transit on a one-year lease for the operator's one-year-long double-decker pilot project. The pilot is part of an exploration of different high-capacity bus types to carry more passengers on the high-demand commuter routes, which are between Strathcona County and Edmonton; an articulated bus is also being evaluated as an alternative and there is no commitment to put any Alexander Dennis model or any double-decker design into permanent service. This bus becomes the first double-decker to be used for regular transit service in Alberta.