The Great Seto Bridge is a series of double deck bridges connecting Okayama and Kagawa prefectures in Japan across a series of five small islands in the Seto Inland Sea. Built over the period 1978–88, it is one of the three routes of the Honshū–Shikoku Bridge Project connecting Honshū and Shikoku islands, and the only one with railroad connections included. At, it ranks as the world's longest two-tiered bridge system. Crossing the bridge takes about 20 minutes by car or train. The ferry crossing before the bridge was built took about an hour. The non-discounted toll from Kojima, Kurashiki to Sakaide is ¥3,500, and vice versa. The bridges carry two lanes of highway traffic in each direction on the upper deck and one railway track in each direction on the lower deck.
History
When in 1889 the first railway in Shikoku - between Marugame and Kotohira - was completed, a member of the Prefectural Parliament, Jinnojo Ōkubo, stated in his speech at the opening ceremony: "The four provinces of Shikoku are like so many remote islands. If united by roads, they will be much better off, enjoying the benefits of increased transportation and easier communication with each other." While it took a century for this vision of a bridge across the Seto Inland Sea to become reality, another of Ōkubo's ideas, mentioned in a drinking song he composed, was accomplished twenty years sooner: The bridge idea lay dormant for about sixty years. In 1955, after 171 lives were lost when a ferry wrecked in dense fog off the coast of Takamatsu, a safer crossing was deemed necessary. By 1959, meetings were held to promote building the bridge. Scientists began investigations shortly after, and in 1970, the Honshu-Shikoku Bridge Construction Authority was inaugurated. However, work was postponed for five years by the "oil shock" of 1973; once the Environment Assessment Report was published in 1978, construction got underway. The project took ten years to complete at a cost of US$7 billion; of concrete and 705,000 tons of steel were used in construction. Although nets, ropes and other safety measures were employed, the lives of 13 workers were lost during the 10 years of construction. The bridge opened to road and rail traffic on April 10, 1988.
Constituent bridges
Six of the eleven bridges are separately named, unlike some other long bridge complexes such as the San Francisco–Oakland Bay Bridge. The other five bridges are viaducts. The six named bridges from north to south are listed below. ;Shimotsui-Seto Bridge: The Shimotsui-Seto Bridge is a double-decked suspension bridge with a center span of and a total length of which connects Honshū with the island of Hitsuishijima. It is the 45th largest suspension bridge in the world. It is the northernmost bridge of the Seto-Chuo Expressway. ;Hitsuishijima Bridge: The Hitsuishijima Bridge is a double-decked cable-stayed bridge with a center span of and a total length of. It is immediately north of the identical Iwakurojima Bridge. ;Iwakurojima Bridge: The Iwakurojima Bridge is a double-decked cable-stayed bridge with a center span of and a total length of. It is immediately south of the identical Hitsuishijima Bridge. ;Yoshima Bridge: The Yoshima Bridge is a continuous double-decked truss bridge with a main span of and a total of five spans with a length of. It is immediately south of the Hitsuishijima and Iwakurojima Bridges. ;Kita Bisan-Seto Bridge: The Kita Bisan-Seto Bridge is a double-decked suspension bridge with two sections linked by a common anchorage between them. The center span is and the total length is. It is the 19thlargest suspension bridge in the world. The nearly identical Minami Bisan Seto Bridge is located immediately to the south. ;Minami Bisan-Seto Bridge: The Minami Bisan-Seto Bridge is a double-decked suspension bridge with a center span of and a total length of. It is the 13th longest suspension bridge span in the world. It is the southernmost part of the Great Seto Bridge. The roadway of the bridge is above sea level.
