[Titles] Various shots into open cab, of engines, of parts of trucks being tested. Sequence showing trucks being driven very slowly over low artificial obstacles to test articulations of axles. Various shots of different type of trucks moving past camera on test courses in field, in woods. Several CUs of wheels turning, some equipped with removable cleats. Shots of trucks stuck in soft soil, mud, CUs of wheels turning to no avail, of trucks pulling themselves out of holes.