Cal. Veh. Code § 13953
In the alternative to the procedure under Sections 13950, 13951, and 13952 and in the event the department determines upon investigation or reexamination that the safety of the person subject to investigation or reexamination or other persons upon the highways require such action, the department shall forthwith and without hearing suspend or revoke the privilege of the person to operate a motor vehicle or impose reasonable terms and conditions of probation which shall be relative to the safe operation of a motor vehicle. No order of suspension or revocation or the imposition of terms or conditions of probation shall become effective until 30 days after the giving of written notice thereof to the person affected, except that the department shall have authority to make any such order effective immediately upon the giving of notice when in its opinion because of the mental or physical condition of the person such immediate action is required for the safety of the driver or other persons upon the highways.
Ca. Veh. Code § 13953