Utah Code § 41-21-3: Minimum speed inapplicable.

The provisions of this title relating to minimum speed provisions upon highways do not apply to vehicles properly registered under Title 41, Chapter 1a, Motor Vehicle Act while the vehicles are being driven to or from an assembly, convention, or other meeting where the vehicles and their ownership are of primary interest, or while they are being driven to or from, or while on local, state, or national tours held primarily for the exhibition and enjoyment of the vehicles by their owners, and so long as the vehicle or group of vehicles are not operated in a manner which would constitute a public nuisance or create a hazard to other automobiles or persons.