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.
Double-decker bus
From March 2009 to June 2012, three imported Alexander Dennis Enviro500 double-decker buses similar to those in Victoria were used on OC Transpo express routes on the Transitway in Ottawa, Ontario. Delivered in November 2008, these buses proved to be efficient in reducing costs, but their height prohibited their use on many routes. Consequently, these three buses were withdrawn and sold to Victoria in late 2012 after a new series of 75 Enviro500 buses with a lower height that met MTO regulations entered service earlier that year. As of 2018 OC Transpo has 133 of these buses.
GO Transit, a regional transit system serving the Greater Toronto Area in Ontario is the largest user of double-decker buses in Canada, with over 150 such vehicles in service as of 2017. Its fleet comprises Alexander Dennis Enviro500s in a single-door, commuter-type configuration similar to its fleet of highway coaches. The first 22 entered service between 2008 and 2009, with its 4.3-metre roof height limiting usage to the Highway 407 corridor. 105 additional buses were delivered between 2012 and 2015 and feature a lower roof height of 4.1 metres. The latest series of 253 buses, which is currently built in a local factory in Vaughan, has a roof height of 3.9 metres and is expected to replace most of the single-decker coach fleet by 2020, at which point 75% of the active fleet is expected to be composed of double-deckers.