Nonetheless, because there are steep inclines and sharp turns on the mountain track, it is not advantageous for long-distance transport, so a coastal line was added in 1919. At Chunan in Miaoli County the main line splits, with one route running through the mountains and the other along the coast. They don't merge again until Changhua.
不過因為山線的坡度及彎度都大，不利於長程運輸，在日據大正八年（一九一九年）又另建一條海線紓解交通，於是從苗栗竹南開始縱貫鐵路一分為二，一條穿山，一條靠海，到彰化再合而為一。