The Hải Vân Tunnel, the longest tunnel in Southeast Asia at 6.28 km, lies on highway 1 between the two cities of Da Nang and Huế in central Vietnam. The Hải Vân Pass has long been recognised as a major bottleneck. The concept of a tunnel to bypass the long route over the top had long been sought.
Route planning and design work started in January 1998 by a joint venture between Nippon Koei Company Limited Japan and Louis Berger International Inc., USA with the Vietnamese Transport Engineering Design Incorporated (TEDI) providing consultation on the project. The project's major constructors were a Vietnam–Japan joint venture, Hazama-Cienco 6, and a joint venture between Korea's Dong Ah construction company and Vietnam's Song Da Construction Corporation.