Where car rentals do the real work
The east coast makes the clearest case. Two routes run south from Hualien towards Taitung — one along the Pacific shore, the other Highway 9 inland through the Rift Valley — with long gaps between towns on both. Then there are the climbs to Sun Moon Lake, Alishan and the high pass at Hehuanshan. Kilometres on a map undersell them: the road bends and gains height almost the whole way, so the driving time runs well past what the distance suggests.