Utah Code § 41-21-4

The provisions of this title relating to minimum safety equipment are not applicable to vehicles properly registered under Title 41, Chapter 1a, Part 2, Registration, so long as the original equipment, on the vehicle at the time of its manufacture, is in good operating condition or has been replaced by equal or more efficient equipment in good working order and the vehicle is not operated in a manner or at a time that would constitute a public nuisance or create a hazard to other automobiles or persons.