Western Trunk Line Coastal Section (Dachia–Changhua)

The Coastal Line (海線, Kaigan-sen) of Taiwan's Western Trunk Railway is a 90.2-kilometer rail corridor running along the western seaboard of the island between Zhunan (竹南) in Miaoli County and Changhua (彰化) in Changhua County. Construction began in 1919 under the Taiwan Governor-General's Railway Department (臺灣總督府交通局鐵道部) and was completed on October 11, 1922, during the Taisho era. The line was built to relieve severe congestion on the original Mountain Line (山線), which passed through the mountainous terrain east of Taichung and suffered from steep gradients, sharp curves, and limited freight capacity.

The decision to construct the Coastal Line was driven by both economic and strategic considerations. By the late 1910s, Taiwan's sugar, rice, and industrial output had grown rapidly under Japanese colonial development, and the single Mountain Line could no longer handle the volume of freight and passenger traffic. Militarily, the Japanese authorities recognized the vulnerability of relying on a single north-south rail corridor that traversed mountainous terrain susceptible to landslides and potential sabotage. The Coastal Line provided a critical backup route through the flat western plains, ensuring that military supplies, troops, and industrial materials could continue moving between northern and southern Taiwan even if the Mountain Line were disrupted.

During the Pacific War (1941–1945), the Coastal Line played an increasingly vital role in Japan's wartime logistics on Taiwan. The island served as a forward staging base for operations in Southeast Asia and the Philippines, and the railway system was essential for moving troops to ports, transporting materials to airfields, and distributing supplies from factories across the island. The flat coastal route was particularly suited to heavy freight operations. Allied bombing campaigns in 1944–1945 targeted Taiwan's railway infrastructure, and having two parallel north-south lines provided operational resilience that proved strategically important.

The Coastal Line is notable for its collection of well-preserved Japanese-era wooden station buildings, several of which have been designated as cultural heritage sites. The most famous are the so-called "Five Treasures of the Coastal Line" (海線五寶): Zhuifen (追分), Rinan (日南),談文 (Tanwen), Dashan (大山), and Xinpu (新埔) stations. These stations, built in the early 1920s in a distinctive Japanese-Western eclectic wooden architectural style, feature hipped roofs with Y-shaped wooden trusses, Western-influenced window designs, and raised wooden platforms. Zhuifen Station, located in Dadu District of Taichung City near where the Coastal Line meets the Taichung Line, is perhaps the most celebrated — its name derives from the Japanese railway term "oiwake" (追分), meaning a point where rail lines diverge.

Today the Coastal Line remains in active service as part of Taiwan Railways' Western Trunk Line, carrying both passenger and freight trains. The heritage station buildings have been restored and serve as popular cultural tourism destinations, offering visitors a tangible connection to Taiwan's Japanese colonial railway heritage and the strategic infrastructure that shaped the island's wartime experience.