http://le.utah.gov/~code/TITLE41/htm/41_06a070400.htm
(2) On a highway having more than one lane in the same direction, the operator of a vehicle traveling in the left general purpose lane:
(a) shall, upon being overtaken by another vehicle in the same lane, yield to the overtaking vehicle by moving safely to a lane to the right; and
(b) may not impede the movement or free flow of traffic in the left general purpose lane.