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.

They also had ticket machines. (PROSE: Just the Ticket)

History
Iris Wildthyme's TARDIS, also known as the Celestial Omnibus, resembled a red London double decker bus, specifically the Number 22 to Putney Common. By one account, Iris found the bus during her youth in the Obverse, where it had crashed, and she 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)

In October 2016, Miss Quill used a double decker bus to drive directly into the trunk of the Lankin, knocking the root that took the form of Tanya's father, Jasper Adeola, out of the window, and causing the Lankin to retreat back in the rift in space and time in a weakened state. (TV: Nightvisiting)

Undated events
Iris Wildthyme and Panda travelled to a warehouse filled with double decker buses, because Iris needed to research the interior dimensions of a conventional bus so she could make the Celestial Omnibus bigger on the inside like it was supposed to be, but the ghost of a ticket inspector who died in the warehouse prevented them from doing so. (PROSE: Just the Ticket)