(4) In accordance with Title 63G, Chapter 3, Utah Administrative Rulemaking Act, the Department of Transportation may make rules to permit the use of tires on a vehicle having protuberances other than rubber, if the department concludes that protuberances do not:

1. (a) damage the highway significantly; or
2. (b) constitute a hazard to life, health, or property.

(5) Notwithstanding any other provision of this section, a person may use:

1. (a) a tire with protuberances consisting of tungsten carbide studs on a vehicle if the studs:

   1. (i) are only used during the winter periods of October 15 through December 31 and January 1 through March 31 of each year;
   2. (ii) do not project beyond the tread of the traction surface of the tire more than .050 inches; and
   3. (iii) are not used on a vehicle with a maximum gross weight in excess of 9,000 pounds unless the vehicle is an emergency vehicle or school bus;
2. (b) farm machinery with tires having protuberances which will not injure the highway; and
3. (c) tire chains of reasonable proportions on a vehicle when required for safety because of snow, ice, or other conditions tending to cause a vehicle to skid.

(6) Notwithstanding any other provision of this chapter, a highway authority, for a highway under its jurisdiction, may issue special permits authorizing the operation on a highway of:

1. (a) farm tractors;
2. (b) other farm machinery; or
3. (c) traction engines or tractors having movable tracks with transverse corrugations on the periphery of the movable tracks.

(7)

1. (a) A person may not operate a vehicle if one or more of the tires in use on the vehicle:

   1. (i) is in an unsafe operating condition; or
   2. (ii) has a tread depth less than 2/32 inch measured in any two adjacent tread grooves at three equally spaced intervals around the circumference of the tire.
2. (b) The measurement under Subsection (7)(a) may not be made at the location of any tread wear indicator, tie bar, hump, or fillet.