Exploration truck

The exploration truck was an experimental land vehicle invented by the Second Doctor. Materialising the TARDIS within a jungle on an Earth-like planet, the Doctor took the truck out to test with his grandchildren, John and Gillian. They soon found a group of Daleks who were constructing metal tracks on which to travel. The Daleks fired at the truck, destroying it, but the Doctor and his grandchildren escaped by swinging on vines to the TARDIS. There, the Doctor used cables connected to the TARDIS' power supply to send a high current through the tracks, destroying the Daleks. (COMIC: Jungle Adventure)

Behind the scenes
The exploration truck is noticeably too big to have fit through the outer door of the police box-shaped TARDIS.