Double decker bus

A double decker bus was a type of bus commonly used in at least London in the 20th and 21st centuries, as a form of public transport. It had two floors.

History
Iris Wildthyme's TARDIS, known as the Celestial Omnibus, resembled a red London double decker bus, specifically the Number 22 to Putney Common. Iris found the bus during her youth in the Obverse, where it had crashed, and breathed new life into it. She left the Obverse in the bus into the universe beyond. (PROSE: Wildthyme Beyond!)

The 200 was an ordinary London double-decker bus that made an extraordinary detour through a wormhole to the planet San Helios in April 2009. It accepted Oyster cards as payment for trips, though the scanner was fooled by the Tenth Doctor's psychic paper. It later gained the ability to fly due to the Doctor's tampering, and Lady Christina de Souza stole it, and flew away, evading the police. (TV: Planet of the Dead)

Miss Quill used a double decker bus to drive directly into the trunk of the Lan Kin, knocking the root that took the form of Tanya's father, Jasper Adeola, out of the window, and causing the Lan Kin to retreat back in the rift in space and time in a weakened state. (TV: Nightvisiting)