National Traffic Fatality and Injury Reduction Act of 1990

National Traffic Fatality and Injury Reduction Act of 1990 - Authorizes the Secretary of Transportation to make grants for traffic safety programs to States which require any person riding a motorcycle to wear a helmet and any driver or front seat passenger of a passenger car to have seat belts properly fastened.

Requires States receiving grants to agree to maintain their average levels of expenditures for traffic safety programs over the preceding two fiscal years.

Prohibits a State from receiving such a grant in more than three fiscal years. Specifies the Federal share of grants and the aggregate amount of such grants to each State.

Sets forth requirements with respect to: (1) States' eligibility for grants; and (2) measurement of compliance with State safety laws.

Eliminates a provision prohibiting a highway safety program approved by the Secretary from requiring that motorcycle operators or passengers 18 years or older wear a safety helmet.

Amends the National Traffic and Motor Vehicle Safety Act of 1966 to authorize the Secretary to conduct or provide assistance to States in promoting the use of safety belts, child safety restraints, motorcycle helmets, and other safety equipment.

Authorizes appropriations.

Directs the Secretary to withhold a certain percentage of Federal-aid highway funds apportionment to any State where it is lawful to: (1) operate or ride a motorcycle without wearing a motorcycle helmet; or (2) occupy a front seating position in a passenger car without using a safety belt or child safety restraint. Provides that such funds shall remain available to such State for a specified period provided for State compliance with safety requirements.