PURPOSE: To improve the travel performance and to minimize the turning radius, by additionally providing means for controlling the positions of a starting wheel, induction wheel and a rotary wheel.

CONSTITUTION: When projecting the lower section of a caterpillar, the ground pressure will function on the caterpillar thus to sink it. The sink is maximized at the tip of the projection, while minimized at the grounding edge and the sink 9' of the caterpillar will vary depending on the condition of the ground face. The downward force 16 is applied on each elements 12W15 of the caterpillar, thereby they perform only the slight rotation and the up-down motion where the downward motion will be determined by the weight of the vehicle to be applied on the element and the holding force of the ground surface. In other word, each element will act in similar manner that the soft land is rolled by a road roller.