The preferred route keys west of Llandovery, then turns south to cross the A40 and the River Towy. It then heads south-west, contained within a side valley away from the Towy valley so it is less visible from areas popular with visitors. Continuing south-west, it keeps to the east of Llangadog and south of Manordeilo to a point near Rhosmaen, north of Llandeilo.