Thiele Highway branches from Horrocks Highway at Gawler Belt on the outskirts of Gawler, north of Adelaide. It goes north-east through undulating cropping country to skirt the east side of Freeling and continues to cross the Light River and enter the former mining town of Kapunda. It crosses the Light River again mid-way between Kapunda and Eudunda. It continues east-north-east from Eudunda down into the Murray Valley and across the plains past a number of small rural local service centres to Morgan, where it meets the River Murray and Goyder Highway.[4] Most of the route is close to the former Morgan railway line.