Eighty per cent of Taiwan's highway traffic is concentrated on the long western plain. The existing west coast highway, which carries 80 % of the north-south bound traffic, will not be able to meet the demands of future transportation and of balanced economic development.
同時，西部走廊地帶交通量約佔台灣全省公路總交通量之百分之八十，其間南北向的交通量，又有百分之八十密集於縱貫線，因此現在的南北縱貫公路不僅不能適應未來交通的運輸需求，尤難配合目前經濟的均衡發展。