(1) A driver may not operate a motor vehicle upon a highway of the state of Montana unless each occupant of a designated seating position is wearing a properly adjusted and fastened seatbelt or, if 61-9-420 applies, is properly restrained in a child safety restraint.
(2) The provisions of this section do not apply to:
(a) an occupant of a motor vehicle who possesses a written statement from a licensed physician, licensed physician assistant, or advanced practice registered nurse, as defined in 37-8-102, that the occupant is unable to wear a seatbelt for medical reasons;
(b) an occupant of a motor vehicle in which all seatbelts are being used by other occupants;
(c) an operator of a motorcycle or a motor-driven cycle;
(d) an occupant of a vehicle licensed as special mobile equipment; or
(e) an occupant who makes frequent stops with a motor vehicle during official job duties and who may be exempted by the department.
(3) The department or its agent may not require a driver who may be in violation of this section to stop except:
(a) upon reasonable cause to believe that the driver has violated another traffic regulation or that the driver's vehicle is unsafe or not equipped as required by law; or
(b) if a person in the vehicle who is under 6 years of age and weighs less than 60 pounds is not properly restrained under 61-9-420 or this section.