Abstract: An aerial lift comprising a wheeled frame having a telescoping boom pivotally and rotatably mounted thereon. A personnel bucket is pivotally secured to one end of the boom for supporting a person therein. An electrical screw-motor apparatus is pivotally secured to and extended between the bucket and the boom. A plurality of mercury switches are mounted on the bucket and are electrically connected to the screw-motor and the source of electrical power so that the screw-motor is automatically actuated responsive to vertical movement of the boom so as to maintain the personnel bucket in a vertical position at all times. The screw-motor also acts as a snubber to prevent undesirable movement of the bucket at work levels.