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.
Lowbridge double-deck bus
At first, there was no viable alternative to the lowbridge design, apart from the use of single-decker bus. However, the lowbridge type started to become obsolete when low-height chassis were developed, which used a dropped-center rear axle to enable the lower deck gangway to be lowered. This enabled a low-height vehicle to be built without the need for the cumbersome seating layout upstairs. The first such design was the Bristol Lodekka which was introduced by Bristol in 1949. It had a height of around compared to a typical height of around for a conventional highbridge double-decker. It was however only available to nationalised bus companies (Bristol itself being part of the state-owned sector at that time). Other low-height double-deckers included the Dennis Loline (a version of the Bristol Lodekka built under licence); the AEC Bridgemaster and Renown; and the Albion Lowlander (a low-height version of the Leyland Titan PD3). The rear-engined Daimler Fleetline and Bristol VR were also low-height chassis. Nonetheless, despite the advent of the low-height chassis, the last lowbridge double-decker was not built until 1968.