Seikan Tunnel (青函トンネル) Project Profile

The Seikan Tunnel is an engineering landmark in global railway infrastructure, providing a fixed link between Japan’s main island of Honshu and the northern island of Hokkaido. As the world’s second-longest railway tunnel and featuring the longest undersea section, it remains a critical artery for passenger and freight transport. Its dual-gauge design is central to the operation of the Hokkaido Shinkansen high-speed rail line, showcasing long-term strategic planning and technical adaptability.

Technical Specifications

The Seikan Tunnel’s design reflects the immense geological and operational challenges of its location. Constructed through a seismically active zone, its structure consists of a main tunnel, a service tunnel, and a pilot tunnel, which was bored first to assess the geology. The main tunnel supports a dual-gauge track system, accommodating both 1,435 mm standard-gauge Shinkansen trains and 1,067 mm narrow-gauge freight trains simultaneously. This is achieved using a triple-rail slab track configuration.

Power and signaling are highly complex. The electrical system must support both the 25kV AC used by the Shinkansen and the 20kV AC used by conventional freight locomotives. To manage this, specialized multi-system rolling stock, such as the Toshiba-built EH800 series electric locomotives, are employed for freight services. For safety, two undersea emergency stations—Tappi Kaitei and Yoshioka Kaitei—are equipped with fire detection systems, smoke extractors, and water spray nozzles, serving as critical refuge points in case of an incident.

Key Takeaways

• Pioneering Engineering: The Seikan Tunnel set global benchmarks for undersea tunnel construction upon its completion, overcoming significant geological challenges in one of the world’s most active seismic regions.
• Strategic National Connector: It serves as the sole fixed link for the Hokkaido Shinkansen, fully integrating Japan’s northern island into the national high-speed rail network and boosting economic connectivity.
• Model of Infrastructure Adaptability: The tunnel was future-proofed with a design that allowed for its eventual upgrade from a conventional line to a dual-gauge high-speed corridor, demonstrating exceptional long-term strategic vision.

Frequently Asked Questions (FAQ)

How fast do trains go through the Seikan Tunnel?
Currently, Hokkaido Shinkansen bullet trains travel through the Seikan Tunnel at a maximum speed of 160 kilometers per hour (100 mph). This speed is limited to safely manage the air pressure difference when passing slower freight trains. Research and development are underway to enable an increase in Shinkansen speeds to 260 kilometers per hour in the future.

Why is the Seikan Tunnel so important for Japan?
The Seikan Tunnel is critically important because it provides a reliable, all-weather land transport link between Honshu, Japan’s largest island, and Hokkaido. It is a vital artery for both passenger travel via the Shinkansen and for freight transport, ensuring a stable supply chain and fostering economic and social integration between the two regions.