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.
OC Transpo
OC Transpo purchased 75 more Alexander Dennis Enviro500 triple-axle double-decker buses in 2012, to replace older 40-foot models purchased from 1997 to 1999. These extra double-decker buses are used mainly on connexion routes. Double-decker buses use about the same amount of fuel as an articulated 60-foot bus, but only take up the same road area as a regular 40 foot bus, meaning they free up space (especially downtown), and provide increased seated passenger capacity for longer connexion bus routes, lowering OC Transpo's operating costs. As a result of the purchase, the 60-foot articulated buses were being moved from connexion routes to Transitway and other mainline routes, replacing the 40-foot models currently used on some trips by those routes. Those 40-foot models will replace the older 40-foot models currently used on local routes. The older 40-foot buses were retired from service. This plan was approved by the Transit Commission on April 20, 2011. The extra 75 Alexander Dennis E500 double-decker buses entered service between fall 2012 and spring 2013.