The Abo Tunnel
The 4.5-kilometer Abo Tunnel connects Nagano and Gifu Prefectures on National Route 158, passing through the Northern Japanese Alps within the borders of Chubusangaku National Park. Despite Nagano and Gifu being neighboring prefectures, the mountains that divide the two regions made travel between them relatively difficult prior to the opening of the tunnel in 1997. Differences in culture and attitudes between residents of Nagano Prefecture, considered to be East Japan, and Gifu Prefecture, marking the beginning of West Japan, still linger today, even after the tunnel’s opening.
Excessive volcanic activity in the mountains underneath the Abo Pass, a mountain crossing on National Route 158 that sits atop the prefectural border, made construction on the tunnel difficult. Initial surveying work began in 1964, decades before the tunnel opened. The design included several sharp curves to avoid drilling into pockets of volcanic gases trapped in the rocks. Work was undertaken at a slow, careful pace; nevertheless, tragedy struck in 1995 when a steam explosion killed four workers. The explosion also affected the nearby Nakanoyu Onsen Inn, which was reopened in 1998 in a different location. The tunnel is open to regular vehicle traffic.
