1. A vehicle suitable for on- and off-road use, provided with a frame (1) with wheels (2, 3) to be driven by the vehicle engine (9), below which frame (1),at each side between the front and rear wheels (2, 3),an auxiliary frame 4 is provided, which auxiliary frames (4) are each provided with guiding wheels (5, 6) to be driven by hydraulic motors with caterpillar tracks (7) guided thereon, and are vertically displaceable in respect of said vehicle frame (1) by means of lifting cylinders (8) arranged near the extremities thereof and adapted to be separately operated, in order to contact said caterpillar tracks (7) with the bottom, control means (11..14) being present for controlling the liquid supply towards the lifting cylinders (8) and the driving motors for the caterpillar tracks (7) in such a manner that:
- the auxiliary frames (4) can be locked in the completely retracted and extended position; and
- in an intermediate position, in which the wheels (2, 3) remain in contact with the bottom, said auxiliary frames (4) are maintained under a pressure which allows the caterpillar tracks (7) to follow inegalities of the bottom, the cater­pillar tracks speed then being adapted to the wheel speed.