壱岐島
One of the new proposals calls for a combination road and rail link from Karatsu on Kyushu Island and terminating at Busan, the second largest city in South Korea. Of the three tunnel routes under consideration, the favoured design was a combination bridge from Karatsu to Iki Island, followed by a 60 km tunnel to the central portion of Tsushima Island, and then a 68 km tunnel roughly westward to Busan at an estimated cost of approximately 10 to 15 trillion yen ($111 billion to $157 billion).