A vehicle or machine is suitable for operation on uneven or inclined surfaces, the vehicle or machine being a forest work unit and including at least three frame parts and two rotational planes, each of which rotational planes is arranged to be formed, in each particular case, on an interface between two successive frame parts of the vehicle or machine. The rotational planes are, in each particular case, planes perpendicular to the longitudinal axis of the vehicle or machine in the neutral position. The frame parts are thus arranged to be mutually rotatable in relation to said rotational plane.
