Hakkoda tunnel, with a length of 26.45km, is the longest
land based double track railway tunnel in Japan, and sixth
longest in the world. It is located in the northern end of
Hakkoda Mountain between Tenmabayashi mura and
Aomori City in Aomori Prefecture in Japan.The tunnel is
part of the Tohoku Shinkansen railway and was
sponsored by Japan Railway Construction, Transport and Technology
Agency (JRTT). It was built as part of the extension of Tohoku
Shinkansen from Hachinohe to Shin Aomori.Tunnel construction began in
August 1998 and was completed in February 2005 using the New
Austrian Tunnelling Method (NATM). Kajima joint venture built the
Otsubo section of the tunnel.