It is the longest of the expressways in the proposed National Expressway System, and, as currently designated, passes through 33 prefectures. It is the only National Expressway in the system currently signed as such. In expressway planning in the 1990s, before the advent of the Japan-Korea Undersea Tunnel, the corridor in Korea was designated NEX-1W, to be distinguished from the Japanese portion of the route, NEX-1E; the two would be connected by ferry service at Busan and Fukuoka. The opening of the Tunnel in 2010 has obviated the need for a distinction, and the two routes and the additional section in China now constitute NEX-1.