New Central Cross-Island Highway

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. 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. In October 1980, due to unfavorable terrain at Shalixi Stream, the junction was relocated to near Tatajia Saddle at 2,500 meters. 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, In 1991, the Executive Yuan permanently canceled the Yuli-Yushan Line. The Shuili-Yushan Line's Dingkan-Shenmu Village section opened in January 1983. 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. 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. == 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. 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. After adjustments, Taiwan Route 18 covers Taibao to Tatajia, commonly called the Alishan Highway. serving as a watershed between the Choshui River and Kaoping River, with tributaries like Nanzixi River, Boboyou Stream, Haomagaban Stream, and Shalixian Stream. The line ends at the junction of Taiwan Route 21 and Taiwan Route 18 at Dongpu Mountain Pass (2,610 meters), a saddle between Dongpu and Lulin Mountains. After crossing the Bazhang River, it winds through the Duzuo Stream valley, climbing from 250 to 1,070 meters, following the Bazhang-Zengwen watershed from Longmei and the Qingshui-Zengwen watershed past Furong Mountain. The upper Zengwen River, known as Houdapu Stream, penetrates into the Alishan mountain range, the riverbed is noticeably narrow, forming a gorge with steep terrain on both sides. Geologically, from the Tatajia Fault to the Gongtian Fault, the Alishan Highway primarily crosses the Nanzhuang Formation, except for the Furong Mountain section's Guandaoshan Sandstone. Between the Gongtian and , it encounters the Zhuolan Formation, Nangang Formation (including Heshe Formation), Jinshui Shale, Shiliufen Shale, and Dawo Sandstone, with synclines, anticlines, and faults, and Dawo Sandstone exposed near Renai Bridge. West of the Chukou Fault, the Bazhang River influences alluvial and terrace deposits, with the in terraces and alluvial deposits beyond the Wuhuliao Bridge. Disasters Post-921 Earthquake data indicates that slopes facing north, west, or south with gradients over 55% and within 200 meters of water systems are prone to collapses. From 1984 to 1994, 95% of collapses were triggered by heavy rain eroding unstable rock layers, concentrated at 20K–25K (41.9%), 55K–60K (39.2%), and 65K–70K (39.2%), with 91% causing road damage. Affected by the Tatou Fault and Gongtian Fault, its fragile rock layers, infiltrated by rainwater, combined with erosion from a Duzuo Stream tributary, cause landslides during typhoons, with an average slide of 1.8 cm annually from May to September. Remediation, including Duzuo Stream bank protection, slope stabilization, and drainage, along with monitoring instruments, has reduced risks. Shuili-Yushan Line The Shuili-Yushan Line, or Shuili-Yushan Section, spans 71 km from in Shuili to Dongpu Mountain Pass, entirely within Nantou County through Shuili and Xinyi Townships. The Dingkan to section (34.3 km) upgraded existing roads, while the Shenmu Village to Dongpu Mountain Pass section (36.7 km) was newly built. It passes Dingkan, Xinshan, , , Xinyi, and . After crossing the Chenyoulan River, it shifts to the west bank, following Heshe Stream's west bank past Heshe, then climbs sharply along the Dongpu Mountain Block watershed from Heshe Stream's east bank to Shalixian Stream's west bank, using hairpin turns through Tongfu Mountain to align with the Dongpu Mountain ridge to Dongpu Mountain Pass. It is part of Taiwan Route 21, known as the "Third Inland Longitudinal Highway" due to its proximity to the Central Mountain Range. Taiwan Route 21 was initially planned from Xindian to Zhuozikiln, now spanning Tianleng to Linyuan, encompassing the Shuili-Yushan Line. From Wuqian Stream to Tatajia, terrain constraints force the highway into multiple hairpin turns, a section geographer Wang Xin calls the "Great Hairpin Bend." At the Dongpu Mountain segment, the route aligns roughly parallel to the ridge. Along the Shuili-Yushan Line, the Chenyoulan River watershed features 16 alluvial fans, later terraced by erosional rejuvenation. Large terraced fans at Xinxian and are among Taiwan's most extensive, supporting settlements. Due to their elevation above the highway, most fans, except for smaller ones near Junkeng, are not fully visible. At Dingkan, the Shuichangliu and Baileng Formations dominate. The Chenyoulan River's numerous alluvial fans result from collapse zones within its watershed. Steep, short valleys, complex geology, and fractured rock layers, combined with upstream erosion, lateral erosion, rainfall, and earthquakes, cause debris to slide or roll into valleys. During typhoons or monsoons, accumulated debris forms mudflows when heavy rain mobilizes it. Insufficient drainage clogs bridge openings, leading to impacts from debris and boulders, causing bridge loss, tilting, or deck displacement. For example, Typhoon Herb destroyed Xinxing Bridge, damaged Xinyi and Junkeng Bridges, clogged Chenyoulan River Bridge's openings, and exposed its piers. Typhoon Toraji washed away one end of Xinyi Bridge and destroyed Chenyoulan River, Songquan, Aiyu, and Shenhe Bridges. Typhoon Sinlaku buried the southern entrance of the Fengqiu-Ming Tunnel, and Typhoon Morakot destroyed the Wuqian Stream Bridge. Riverbank erosion, driven by tributary sediment clogging the main channel, reduces channel capacity, redirects flow, and accelerates erosion, causing bridge foundation collapses, as seen with Xinyi, Shiba Stream, and Chenyoulan River Bridges during Typhoons Herb and Toraji. River meandering, such as Bishi Stream's redirection during Typhoon Toraji, severed the highway by cutting a straighter path into the Chenyoulan River. Sections like Xingaokou, Shishan, and Tatajia, near ridges, experience minor debris falls, while other segments are prone to rockfalls. The Wuqian Stream Valley's cirque-like collapse zone and faulted, fractured rock layers, eroded by heavy rain, supply debris for mudflows. Initially planned at 102.7 km (7.1 km of existing roads upgraded, 95.6 km newly built), it was later revised to 122 km (7.2 km upgraded, 114.8 km newly built). The route spanned Xinyi Township, Nantou; Taoyuan District, Kaohsiung; and and Yuli Townships, Hualien. Planned to converge with the Chiayi-Yushan and Shuili-Yushan Lines at Dongpu Mountain Pass, construction halted after 14.6 km, leaving Dongpu Mountain Pass, now called Tatajia, as the junction of only the Chiayi-Yushan and Shuili-Yushan Lines. Plan overview The original route started at the three-line junction, passing Saddle and Shalixi Stream, navigating terrain to reach the highway's highest point at Batongguan (2,800 meters). ending at Yuli with Taiwan Route 9. Geologically, it followed the Batongguan Historic Trail through the Dananao Schist, divided into the Tailuge Formation and Yuli Formation, comparable to the Central Cross-Island Highway's Tianxiang Formation, Changchun Formation, and Jiuju Marble. The route also crosses the Bilu Mountain Formation's slate belt between the Dananao Schist and alluvial layers. Yuli, at the Huadong Valley's center and lies at the confluence of Lakulaku, Xiuguluan, and Zhuoxi Streams, with alluvial deposits from Lakulaku and Qingshui Streams. == Natural resources ==

Spanning Chiayi, Nantou, and Hualien, the New Central Cross-Island Highway aimed to leverage mountain resources for economic growth. Surveys identified the Alishan Coalfield along the Chiayi-Yushan Line, with 600,000 tonnes of high-quality coal in the Nanzhuang Formation, fragmented by faults and folds, yielding up to 100,000 tonnes due to low mining efficiency. The Shuili-Yushan Line lacks significant resources, though nearby indicate geothermal potential, deemed inefficient due to remoteness and low yield (less than 2% of Taiwan's power needs). The Yuli-Yushan Line, planned through Batongguan to , holds the most resources, including crystalline limestone (marble), dolomite, quartz schist, and gold-bearing quartz veins. Walami's 5 billion tonnes of marble offer the greatest mining potential, though high-quality marble is limited. The Taiwan Power Company considered hydropower from Lakulaku and Chenyoulan Streams, primarily Lakulaku, but limited data restricts further assessment. == Ecology ==

Flora From September 1987 to January 1988, professors Yang Shengren, Qiu Chuangyi, and Ye Qinglong from Pingtung Agricultural College (now National Pingtung University of Science and Technology) surveyed the highway's flora, identifying seven forest types by dominant and characteristic species, from low to high altitude: Miscanthus floridulus type, Artemisia-Japanese knotweed type, Taiwan red cypress type, Morrison's maple type, Formosan alder type, Taiwan pine type, and Formosan eupatorium type, widely distributed from lowlands to high mountains. At 350–1,300 meters, Miscanthus dominates with Hibiscus mutabilis, kudzu, and ramie, visible from Chukou to Alishan, replaced by Japanese cedar plantations above 1,400 meters. The park's management commissioned ecological surveys, supplemented by nearby , , , and . Formosan macaques maintain static behavior at over two meters from humans, but at less than one meter with frequent or aggressive interaction, they may rob food or attack, commonly seen at Shishan with rope bridges for safe crossing. Formosan black bears inhabit needle and broadleaf forests below 3,000 meters, primarily in Walami and Dafen, with sightings near Menglu Pavilion and Tatajia during quiet periods, indicating human activity's impact. Swinhoe's pheasant (Class II protected) and Formosan serow (Class III protected) avoid human disturbance, foraging along roads during low traffic or foggy conditions. == Transportation network ==

The New Central Cross-Island Highway comprises the Chiayi-Yushan, Shuili-Yushan, and Yuli-Yushan Lines. The unbuilt Tatajia to Shanfeng section isolates the Chiayi-Yushan and Shuili-Yushan Lines as a standalone system, while the Yuli-Yushan Line integrates with eastern Taiwan's network via Taiwan Route 30 with the Yuchang Highway. it into northern and southern segments, limiting north–south connectivity. the Shuili-Fenglin Line was more cost-effective than the New Central Cross-Island Highway due to shorter new sections. The highway lost its east–west traversal role, with the Central and Southern Cross-Island Highways serving Yuli to Shuili or Chiayi. From western Taiwan to Yuli, routes include a northern detour via Dingkan, Puli, , Dayuling, , and Taiwan Route 9, or a southern detour via Alishan Highway to Longxing or Jiayi 129 Line to Shixiangnei. Both routes connect to Taiwan Highway 3. Heading south along Highway 3, pass through Dapu and Yujing to Beiliao, where it connects to Highway 20. Then continue to Chulai, turn north across the , follow Highway 20A to Chishang, connect to Highway 9 heading north, and finally arrive at Yuli. == Medical services ==

Since opening, the New Central Cross-Island Highway has been vital for mountain medical and rescue operations, serving remote townships like Xinyi and Alishan. Its winding, high-altitude roads increase travel time and risks, and limited local development results in scarce medical resources, complicating emergency responses. At the Walami Trailhead in Yushan National Park's eastern zone, Taiwan Route 30 is 15 km from Yuli, home to Tzu Chi Hospital, Yuli Veterans Hospital, and Ministry of Health and Welfare Yuli Hospital. The Xianglin Joint Clinic in serves , , and Xianglin, handling tourist emergencies with adequate equipment but no resident EMT. It is staffed by nurses and weekend doctors, with a helipad for evacuations. The Alishan Medical Station at Shizhuo, staffed daily by doctors from St. Martin De Porres Hospital, addresses local medical shortages but lacks advanced emergency resources, relying on helicopter evacuations. == Tourism ==

Natural attractions Taiwan Route 18, commonly known as the Alishan Highway, ascends from Chiayi to Alishan, traversing four forest belts—tropical, warm, temperate, and cold—due to elevation changes. earning them the designation of a fog forest belt. The route is home to numerous giant trees, revered as sacred, including over 30 along Alishan's boardwalk, as well as the Shuiku Sacred Tree, Lulin Sacred Tree, Upper Dongpu Great Hemlock, and Wannian Sacred Tree at Shenmu Village. The highway also offers stunning natural vistas, including sunrises, cloud seas, and sunsets, with Duigaoyue and Zhushan as renowned viewing spots. At Tatajia, Yushan National Park features a recreation area surrounded by peaks such as Dongpu Mountain, Lulin Mountain, Lulin Front Mountain, and Linzhi Mountain. The junction of Taiwan Route 18 and Taiwan Route 21 forms the Dongpu Mountain Pass, a saddle between Dongpu and Lulin Mountains. The Yushan National Park Administration has designated the segment from Taiwan Route 18's 105.2K to Taiwan Route 21's 119.5K as a scenic highway, marked by the park's boundary monument. Attractions along this route include Guanshan, Guanfeng, and the Couple Trees, with autumn showcasing the vibrant, changing foliage of Morrison's maple and falling leaves. On Taiwan Route 30, the , located close to the highway, is just a 2-km drive from the Nanan Visitor Center, making it a highlight of the . The Dongpu Hot Spring area connects to the highway via County Route 60, linking to external transport and forming a key tourism route, with the nearby Lele Valley Hot Spring as an additional attraction. Cultural attractions The Batongguan Historic Trail, now a hiking route maintained by the Yushan National Park Administration, was completed by Japanese authorities in 1921. A monument commemorating the trail's construction stands in front of the Nanan Visitor Center, with the trail's eastern section partially designated as the Walami Trail. The Walami Trailhead connects to Taiwan Route 30, a remnant of the stalled Yuli-Yushan Line. The “Xingaokou” (New High Mouth), the historical Japanese-era climbing entrance to New High Mountain (now Yu Shan), is located at the Tatajia Saddle. A stone monument marking the “New High Climbing Entrance” stands in Dingkan Village's Zhentou Lane, the Japanese-era gateway to New High Alishan, designated by the Taiwan Governor-General's Office as a national park candidate site. The Tatajia Visitor Center, situated at the planned junction of the New Central Cross-Island Highway's three lines, now serves as the intersection of Taiwan Route 18 and Taiwan Route 21, where the Yuli-Yushan Line's construction was halted. Longyin Temple, built in 1980 at , Fanlu Township, along Taiwan Route 18, is the newest, dedicated to Master Jigong. Nearby, the Tianchang and Dijiu Suspension Bridges, collectively called “Tianchang Dijiu” (Everlasting), are located near Longyin Temple. The Dijiu Bridge spans Bazhang Stream, parallel to the Chukou Bridge on Taiwan Route 18. Before the Alishan Highway's construction, these bridges were the primary access route for residents traveling between Gongtian and Chukou. Following the Alishan Highway's completion, tea cultivation flourished along the route, reaching saturation in the 1990s. Below Shizhuo, the landscape is dominated by tea gardens. Along Taiwan Route 21 in Shuili and Xinyi, attractions include the , Caopingtou Tourism Tea Garden, and fruit orchards in Shang’an and Fengqiu, alongside wineries and factories for green plums, a local agricultural specialty. During plum blossom season, visitors can witness blooming plum trees in areas like Fengguidou and Wusonglun. == See also ==