Abstract: A vibratory road roller has a drum adapted to be vibrated as it rolls along the ground, to this end the drum containing a vibrator device of the type which produces a vibratory effect as a result of rotation of an out-of-balance mass. The vibrator device comprises a casing, fixed to an end plate of the drum, and a rotor which has a fluid-containing cavity with the contained body of fluid contacting a swept internal annular surface of the casing. A piston movable radially in the rotor and/or the body of fluid provides the out-of-balance mass, and the vibratory force is transmitted to the casing and hence to the drum by the fluid pressure acting on the swept annular surface of the casing. The rotor structure itself is mechanically balanced so that substantially no vibratory force is transmitted through the rotor shaft and bearings.