321.311  Turning at intersections.
  1.  The driver of a vehicle intending to turn at an intersection shall do so as follows:
  a.  Both the approach for a right turn and right turn shall be made as close as practical to the right-hand curb or edge of the roadway.
  b.  Approach for a left turn shall be made in that portion of the right half of the roadway nearest the center line thereof and after entering the intersection the left turn shall be made so as to depart from the intersection to the right of the center line of the roadway being entered.
  c.  Approach for a left turn from a two-way street into a one-way street shall be made in that portion of the right half of the roadway nearest the center line thereof and by passing to the right of such center line where it enters the intersection. A left turn from a one-way street into two-way street shall be made by passing to the right of the center line of the street being entered upon leaving the intersection.
  2.  Local authorities in their respective jurisdictions may cause markers, buttons, or signs to be placed within or adjacent to intersections and thereby require and direct that a different course from that specified in this section be traveled by vehicles turning at an intersection, and when markers, buttons, or signs are so placed no driver of a vehicle shall turn a vehicle at an intersection other than as directed and required by such markers, buttons, or signs.
[S13, §1571-m18; C24, 27, 31, 35, §5033; C39, §5025.01; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §321.311]
For applicable scheduled fine, see §805.8A, subsection 6
Additional penalties for violations causing serious injury or death, see §321.482A