Utah Code § 41-6a-1614
Head lamps on farm tractors -- Motor vehicles sold prior to certain date.
(1) Head lamp systems which provide only a single distribution of light shall be permitted on: (a) a farm tractor; and (b) other motor vehicles manufactured and sold prior to July 1, 1980. (2) Head lamp systems authorized under this section shall comply with rules made by the department under Section 41-6a-1601.