Usui Bridge (Japanese: 碓氷第三橋梁, Usui Daisan Kyōryō), also commonly known as Megane-bashi (めがね橋, "Spectacles Bridge"), is the largest brick-masonry arched bridge in Japan. It is located over the Usui River in Annaka City, Gunma Prefecture, Japan.
Construction and Design
The bridge was completed in December 1892 and was built for the Usui railway line, which connected Yokokawa in Gunma Prefecture to Karuizawa in Nagano Prefecture. It was designed by British engineer Charles Assheton Whately Pownall during the Meiji era, in collaboration with Japanese engineer Seiichi Furukawa. The bridge measures 91 meters (299 ft) in total length and reaches a height of approximately 31 meters (102 ft) from the river bottom. It was constructed using approximately 2 million bricks.
Architecture and Nickname
The bridge features four arches, and its nickname "Megane-bashi" (Spectacles Bridge) derives from the resemblance of these arches to a pair of eyeglasses.
History and Railway Use
The bridge served as part of the Shin'etsu Main Line, supporting the Abt rack railway system that was introduced to overcome the steep 66.7 per mille gradient of the Usui Pass. The Abt system used a toothed rack rail between the running rails, allowing trains to safely navigate the steep incline. The line operated from 1893 until railway services ceased in 1963, when a new electrified line was constructed.
Cultural Heritage and Current Use
In 1993, the Usui Bridge was designated a National Important Cultural Property of Japan as part of the "Usui Pass Railway Facilities." In 2001, the former railway line was converted into a 6-kilometer walking trail called "Abt Road" (Apt Road), allowing visitors to walk across the bridge and through the surrounding tunnels. The bridge is also recognized as a Modern Industrial Heritage Site by Japan's Ministry of Economy, Trade and Industry.
