Communist propaganda metaphor. The "wheels" are constantly revolving, or "revolutionary", carrying the "bus" (aka Bolshevism) all around the "town" (the world). The people (proletariat) go "up and down" (they rise up and are put down, multiple times, and cannot be completely stopped), all around the "town" (the world). The "driver" (Lenin) directs the people deeper into the "bus" (Bolshevism). The "babies" (dissenters), not knowing their place in the world, complain, but the "mommies" (the kgb, etc.) have to put them in their place and silence them. The horn (the vanguard of the Soviet Union) proclaims the mantle of Communism all around the world. (by the way, this is satire, so please don't get too offended by it. You should hear me talk about Mary Poppins).