307.178.  Seat belts required for passenger cars — passenger cars defined — exceptions — failure to comply, effect on evidence and damages, admissible as evidence, when — penalty — passengers in car exceeding number of seat belts not violation for failure to use. — 1.  As used in this section, the term "passenger car" means every motor vehicle designed for carrying ten persons or less and used for the transportation of persons; except that, the term "passenger car" shall not include motorcycles, motorized bicycles, motor tricycles, and trucks with a licensed gross weight of twelve thousand pounds or more.

  2.  Each driver, except persons employed by the United States Postal Service while performing duties for that federal agency which require the operator to service postal boxes from their vehicles, or which require frequent entry into and exit from their vehicles, and front seat passenger of a passenger car manufactured after January 1, 1968, operated on a street or highway in this state, and persons less than eighteen years of age operating or riding in a truck, as defined in section 301.010, on a street or highway of this state shall wear a properly adjusted and fastened safety belt that meets federal National Highway, Transportation and Safety Act requirements.  No person shall be stopped, inspected, or detained solely to determine compliance with this subsection.  The provisions of this section and section 307.179 shall not be applicable to persons who have a medical reason for failing to have a seat belt fastened about their body, nor shall the provisions of this section be applicable to persons while operating or riding a motor vehicle being used in agricultural work-related activities.  Noncompliance with this subsection shall not constitute probable cause for violation of any other provision of law.  The provisions of this subsection shall not apply to the transporting of children under sixteen years of age, as provided in section 307.179.

  3.  Each driver of a motor vehicle transporting a child less than sixteen years of age shall secure the child in a properly adjusted and fastened restraint under section 307.179.

  4.  In any action to recover damages arising out of the ownership, common maintenance or operation of a motor vehicle, failure to wear a safety belt in violation of this section shall not be considered evidence of comparative negligence.  Failure to wear a safety belt in violation of this section may be admitted to mitigate damages, but only under the following circumstances:

  (1)  Parties seeking to introduce evidence of the failure to wear a safety belt in violation of this section must first introduce expert evidence proving that a failure to wear a safety belt contributed to the injuries claimed by plaintiff;

  (2)  If the evidence supports such a finding, the trier of fact may find that the plaintiff's failure to wear a safety belt in violation of this section contributed to the plaintiff's claimed injuries, and may reduce the amount of the plaintiff's recovery by an amount not to exceed one percent of the damages awarded after any reductions for comparative negligence.

  5.  Notwithstanding any other provision of law to the contrary, subsection 4 of this section shall not apply to any action arising out of the design, construction, manufacture, distribution, or sale of a motor vehicle, as defined in section 301.010, factory-equipped with a safety belt.  In such actions arising out of the design, construction, manufacture, distribution, or sale of a motor vehicle, a plaintiff's failure to wear a properly adjusted and fastened safety belt shall be admissible as evidence of comparative negligence or fault, causation, absence of a defect or hazard, and failure to mitigate damages.

  6.  Except as otherwise provided for in section 307.179, each person who violates the provisions of subsection 2 of this section is guilty of an infraction for which a fine not to exceed ten dollars may be imposed.  All other provisions of law and court rules to the contrary notwithstanding, no court costs shall be imposed on any person due to a violation of this section.  In no case shall points be assessed against any person, pursuant to section 302.302, for a violation of this section.

  7.  The state highways and transportation commission shall initiate and develop a program of public information to develop understanding of, and ensure compliance with, the provisions of this section.  The commission shall evaluate the effectiveness of this section and shall include a report of its findings in the annual evaluation report on its highway safety plan that it submits to NHTSA and FHWA pursuant to 23 U.S.C. Section 402.

  8.  If there are more persons than there are seat belts in the enclosed area of a motor vehicle, then the passengers who are unable to wear seat belts shall sit in the area behind the front seat of the motor vehicle unless the motor vehicle is designed only for a front-seated area.  The passenger or passengers occupying a seat location referred to in this subsection is not in violation of this section.  This subsection shall not apply to passengers who are accompanying a driver of a motor vehicle who is licensed under section 302.178.