An optical axis control assembly is provided with a plurality of control
means which are supplied with information necessary for deciding the tilt
angle of the car body 1, and determine the body tilt angle by sharing the
input information with the other control means; and optical axis control
means for controlling the optical axis of each headlight based on the
determined body tilt angle. By the combined use of a plurality of
low-cost, small control devices of the same specifications each of which
is incapable of determining the body tilt angle by itself because of a
lack of information, the optical axis control device assembly exerts the
function of determining the body tilt angle, and effects the optical axis
control of the headlights based on the determined body tilt angle.