The New Central Cross-Island Highway, also known as the New Central Trans-Island Highway, is an incomplete highway in Taiwan intended to connect the east and west across the central region of Taiwan Island. Positioned between the Central Cross-Island Highway and the Southern Cross-Island Highway, it centers on Jade Mountain and branches into three routes: Chiayi–Yushan, Shuili–Yushan, and Yuli–Yushan, forming a Y-shaped road network. Although designed around Yu Shan, the actual junction was initially planned at Shalixi Stream, later adjusted to Dongpu Mountain Pass, and is now known as , the highway's highest point at 2,610 meters.
In the 1970s, during the Ten Major Construction Projects, the Republic of China government planned to build three new cross-island highways,According to “After the Completion of the Ten Major Construction Projects, It Was Decided to Proceed with Twelve More Projects”, both terms — “three newly constructed cross-island highways” and “three newly constructed east–west cross-island highways” — were used . This explains why the highways are sometimes referred to as the “three newly constructed cross-island highways” and other times as the “three newly constructed east–west cross-island highways.” listed as one of the . By the 1980s, construction of the New Central Cross-Island Highway faced challenges due to growing ecological awareness and the establishment of Yushan National Park along its route, creating a turning point between highway development and environmental conservation. After six years of policy indecision, construction was briefly permitted to extend westward to According to Lin Shiman’s consultation of Ronggong Bulletin, issue no. 928, front page, the construction project of the New Central Cross-Island Highway began in 1981 and was entirely undertaken by the Retired Servicemen Engineering Agency. by the Veterans Engineering Agency (now Retired Servicemen's Engineering Agency). However, following an Environmental Impact Assessment, the Executive Yuan issued an order to abandon construction, resulting in partial completion and the highway opening on January 1, 1991, as a "highway without full traversal."
History
Background and origin On September 20, 1974, recognizing that the existing three east–west cross-island highways were insufficient for regional development, the Executive Yuan planned to construct three additional highways in northern, central, and southern Taiwan to promote balanced regional growth. On September 23, 1977, these were included in the Twelve Major Construction Projects, to be implemented after the Ten Major Projects were completed. The rugged terrain between Chiayi and Yuli, located in central Taiwan and the Huadong Valley, necessitated reliance on the Central or Southern Cross-Island Highways. The New Central Cross-Island Highway was proposed to improve connectivity, reduce transportation distances, and stimulate prosperity in eastern Taiwan for balanced development. Additionally, the route's rich mountain resources supported forestry, agriculture, and mining, while its scenic alpine landscapes and diverse forests, combined with the Third Inland Longitudinal Highway plan, linked attractions like Sun Moon Lake, Alishan, and Zengwen Dam, forming a tourism corridor.
Construction process
Route selection and survey
The Taiwan Provincial Highway Bureau selected routes using 1:50,000 topographic maps, identifying lines including Wulai-Yilan Line, Wushe-Tongmen Line, Shuili-Fenglin Line, Chiayi-Yuli Line, and Sandimen-Zhiben Line. The Chiayi-Yuli Line, the New Central Cross-Island Highway, required the most surveyors and the longest route. On October 15, 1975, a survey team of 14 units started from Heshe, following the Batongguan Historic Trail, bypassing the ridge route from Dashuiku, and proceeding along Laonong Stream. The route crossed the Central Mountain Range between and Jianshan, followed Kuokuosi Stream, passed through , and descended along Lakulaku River, reaching Yuli on October 25. Communication during the survey relied on carrier pigeons.
Plan evolution The Shuili-Yuli Line's section through Xinyi Township was deemed as economically significant as the Chiayi-Alishan road. To facilitate construction, the Chiayi-Yushan Line was incorporated, extending eastward from Alishan to connect with the original route, forming the prototype of the three-line highway. In May 1978, the Executive Yuan approved the Chiayi-Yushan, Shuili-Yushan, and Yuli-Yushan Lines, with a total length of 265.6 km and a budget of NT$3.62 billion, expecting completion in six years. The addition of the Chiayi-Yushan Line led to the establishment of the New Cross-Island Highway Engineering Office in October 1978, dispatching a survey team to the Chiayi-Yushan Line in November. In April 1979, route finalization began, with the junction planned at Shalixi Stream at 2,100 meters. Due to urgent needs, improvements to the Chiayi-Alishan section of the Chiayi-Yushan Line started in 1977. Construction on the Chiayi-Yushan Line began in September 1979, followed by the Shuili-Yushan Line in January 1980.Regarding the start date of construction on the Shuili–Yushan route, in Ye Zhaoxiong’s article "The Development of the New Central Cross-Island Route and the Abandonment Process of the Yuli–Yushan Segment", it is recorded as July 1979. In October 1980, due to unfavorable terrain at Shalixi Stream, the junction was relocated to near Tatajia Saddle at 2,500 meters. In November 1980, surveys revealed that both the Chiayi-Yushan and Shuili-Yushan Lines passed close to , raising maintenance concerns. The junction was finalized at Dongpu Mountain Pass at 2,610 meters, shortening the Chiayi-Yushan Line by 7.5 km.
Conservation and development
Construction on the Yuli-Yushan Line began in July 1981. With 97 km planned through Yushan National Park, rising ecological concerns drew attention from the public and academia. In June 1983, to comply with the Ministry of the Interior's three principles—no routes above 2,600 meters, avoiding Batongguan, and bypassing Yushan National Park—the Taiwan Provincial Highway Bureau proposed three routes from Tatajia Saddle to Dafen. Only the fourth route, along a forest road through Meilan Saddle to Meishankou connecting to the Southern Cross-Island Highway, met these criteria, but it was deemed inefficient. An environmental impact assessment by the concluded that construction would cause environmental damage, including soil erosion, and conflict with Yushan National Park's conservation goals. The Taiwan Provincial Government decided to abandon the project. On April 3, 1986, the Executive Yuan halted the Yuli-Yushan Line, and on May 31, 1989, deferred any resumption pending further evaluation. In 1991, the Executive Yuan permanently canceled the Yuli-Yushan Line.
Completion and opening
The Chiayi-Yushan Line's Chiayi-Alishan section was completed and opened on September 30, 1982. The Shuili-Yushan Line's Dingkan-Shenmu Village section opened in January 1983. The Chiayi-Yushan Line was fully completed in June 1986. The Shuili-Yushan Line faced delays due to geological sliding at the 47K–53K section, completing in December 1990 and opening on January 1, 1991. This connected Chiayi and Shuili, but the Yuli-Yushan Line's interruption left Dongpu Mountain Pass, now Tatajia, as the junction of the Chiayi-Yushan and Shuili-Yushan Lines, with the Shuili-Yushan Line designated as the southern section of Taiwan Route 21, extending over 390 km.
Maintenance To address road and bridge disruptions from typhoons and heavy rain, the Directorate General of Highways began rehabilitation in 2002, dividing the Taiwan Route 21 95K–114K section into two projects. The Shiba Stream Bridge, , and Bishishi Bridge started construction in December 2003, followed by Songquan, Shenhe, and Aiyu Bridges in March 2004, using long-span box steel beams. On October 26, 2006, these six bridges were completed. Due to mudflows and slope collapses at the southern end of the Fengqiu-Ming Tunnel, the Directorate planned the "Taiwan Route 21 Fengqiu-Ming Tunnel Bridge Reconstruction" in 2006.
On January 9, 2007, to accommodate the opening of the Yuchang Highway, a 15 km section of Taiwan Route 18 was merged into Taiwan Route 30. In June 2007, to align with the opening of Chiayi HSR Station, the Directorate extended the Alishan Highway's starting point westward, increasing its length by nearly 14 km to 109.9 km, ending at Tatajia. On September 14, 2008, Typhoon Sinlaku destroyed the Wuhuliao Bridge. In March 2009, reconstruction of the Wuhuliao Bridge began 300 meters downstream, completed on July 31, 2010. On March 27, 2009, the Fengqiu-Ming Tunnel bridge project was completed, renaming the Shalidong Bridge to Shalidong Bridge.
Route description
Initially, the highway was planned to start in Shuili, Nantou, passing through Shalixi Stream and , and ending in Yuli, Hualien. The Chiayi-Yushan Line was later included due to the economic importance of the Chiayi- road, with the three lines—Chiayi-Yushan Line, Shuili-Yushan Line, and Yuli-Yushan Line—forming a Y-shaped network converging at Shalixi Stream. The Chiayi-Yushan and Yuli-Yushan Lines, spanning approximately 204 km, were intended to connect eastern and western Taiwan across the island's central region.Before the adjustment, the original Chiayi–Yushan Line and Yuli–Yushan Line were incorporated into Provincial Highway No. 18. According to the 60th Anniversary Special Issue of the Directorate General of Highways, published in 2006, the total mileage from Chiayi to Yuli along Highway No. 18 was . Since adjustments to Highway No. 18 began in 2007, the most recent documented mileage before the adjustment has been cited. After multiple revisions, the current highway is described below.
Chiayi-Yushan Line The Chiayi-Yushan Line, also known as the Chiayi-Yushan Section, stretches 90.2 km from in Chiayi to Dongpu Mountain Pass. It traverses Zhongpu, Fanlu, Zhuqi, Alishan, and Xinyi Township, Nantou. The route is divided at into lowland and mountain sections: west of Chukou (16.8 km) involves upgraded existing roads through Houzhuang, Geology Along the Route from Chukou to Tatajia Saddle on the New Central Cross-Island Highway in Taiwan, and , crossing Bazhang River to Chukou; east of Chukou (73.4 km) is mountainous, with new sections at 20K–24K, 60K–66K, and from 72K using a former logging railway, passing Chukou, Longmei, , , , Alishan, , and Xingaokou to Dongpu Mountain Pass. Upon completion, it was incorporated into Taiwan Route 18 with the Yuli-Yushan Line.The designation of Provincial Highway No. 18 follows the numbering system established by the Directorate General of Highways, in which east-west routes are assigned even numbers. After adjustments, Taiwan Route 18 covers Taibao to Tatajia, commonly called the Alishan Highway.
Geography