A bulldozer was a vehicle used for moving large amounts of material, such as earth.
The Third Doctor arrived in 2971 after he was asked by millionaire John Henderson to test-drive his time-travelling bulldozer into the future. (COMIC: The Kingdom Builders)
Brodie counted five bulldozers being brought to the Butler Institute's construction site in the Catskill Mountains. (PROSE: Cat's Cradle: Warhead)
In the wake of Miracle Day in 2011, Tutsi in Rwanda bashed the heads of Hutu villagers with clubs and ran over them with bulldozers. (TV: Rendition)
In a jungle, the Quarks attacked the Second Doctor and Jamie McCrimmon. They defended themselves from the Quarks with bulldozers. When the Quarks were later driven off, the Doctor used one of the bulldozers to excavate the TARDIS from the rubble under which it was buried. (COMIC: Jungle of Doom)