The Japanese railway system is once again attracting worldwide attention thanks to one of its most impressive routes: the undersea section that forms part of the Shinkansen line and crosses the Tsugaru Strait. Although it was built several decades ago, the technical scale and precision of this work continue to place it among the great milestones of railway engineering.
This underground tunnel is part of the Seikan Tunnel, a corridor connecting the islands of Honshu and Hokkaido under the sea. Since its inauguration in 1988, the structure continues to be a benchmark for its exceptional length and the complexity of the work carried out at depths that few transport projects in the world have reached. The discovery of the century: this new clean and infinite energy will replace nuclear power, and China could have it in 5 years. They demand the immediate withdrawal of Colombia’s most famous milk from all supermarkets and shops in the country. Opens in a new tab. With more than three decades of operation, the section demonstrates how Japan has managed to unite two territories separated by the sea through stable, safe infrastructure designed for extreme conditions.
Highlights of the Seikan Tunnel
- Total length: 53.85 kilometres.
- Includes 23.3 kilometres of underwater track, one of the longest in the world.
- It is located 140 metres below the seabed.
- Connects Aomori (Honshu) to Hokkaido.
- Its construction began in 1971 and was completed in 1988.
How the Shinkansen undersea section works
The Seikan Tunnel was designed to allow the passage of high-speed trains and freight trains. Its structure includes a triple track system prepared for the circulation of the Hokkaido Shinkansen. Although speed within the undersea section is controlled, the service maintains the operational precision that characterises the Japanese network. The tunnel also has special stations under the sea: Tappi Kaitei and Yoshioka Kaitei, built as emergency points and equipped with ventilation, alarms and fire protection systems. These stations were the first in the world to be located completely below sea level.
A project that marked a turning point in Japanese engineering
The construction of the tunnel crossed seismic zones and required complex techniques. To complete the project, almost 2,900 tonnes of explosives and more than 168,000 tonnes of steel were used. Its interior maintains a stable temperature of 20 °C and a humidity of around 90%. Today, around 50 trains per day run through the Seikan, including freight and passenger services. Since 2016, the section has also allowed the passage of the Shinkansen, which has consolidated its importance within the national railway system.