Crossing the Bohai Strait the tunnel would be 123 kilometers (76 mi) long, 90 kilometers (56 mi) of it under water. This would exceed the combined lengths of the two longest undersea tunnels on Earth, the Seikan Tunnel and the Channel tunnel.
The planned high speed railway would traverse Bohai Bay, connecting Dalian in the south of Liaoning province with the Shandong province city of Yantai. "It will reduce travel time across Bohai Bay to a mere 40 minutes," Wang commented.
At present, a ferry ride across the bay takes about eight hours, while travelling between the two cities by vehicle means covering 1,400 kilometers of coastal roads.
A tunnel between Hong Kong-Macau-Guangzhou-Shenzhen and Zhuhai was considered but Hong Kong Macau bridge is being built instead.
This tunnel will be building experience for even longer tunnels.
The Taiwan Strait Tunnel Project is a proposed undersea tunnel to connect Pingtan in China to Hsinchu in Taiwan as part of the G3 Beijing–Taipei Expressway It would be 150 kilometers long.
A tunnel could link Incheon, South Korea and Weihai of Shandong Province. They are about 340 kilometers apart.
A Bering Strait tunnel would not be as long relative to the other big tunnel projects. A Bering Strait tunnel would be about 103-kilometers (64 mi) long. The Bering strait is no deeper than 55 meters.
With the two Diomede Islands between the peninsulas, the Bering Strait could be spanned by three bridges. Two long bridges, each almost 40 kilometers (25 mi) long, would connect the mainland on each side to one island, and a third much shorter one between the two islands.