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.
Neoplan
In 1964, the founder's second son, Konrad Auwärter, developed a double-deck bus design for a service bus as part of his dissertation. The 'Do-Bus' design had low weight, and could carry over 100 passengers. It also featured a low-frame front axle with forward-mounted steering gear that permitted a low flat floor. The double-deck principle was applied to the coach design, creating a high-capacity comfortable touring vehicle. This vehicle was known as the Skyliner.