Pingtung City
In Tainan City, the highway goes through Nansi, Yujing, and Nanhua. The highway has a concurrency with PH 20 from Yujing to Nanhua before the latter turns east and becomes Southern Cross-Island Highway (南部橫貫公路). The highway then enters Kaohsiung City, passing through the downtowns of mountainous districts of Neimen and Cishan. Highway 3 goes through Jiuru and Ligang in Pingtung County before ending at the intersection with PH 1 in Pingtung City.