The Yamate Tunnel is the world’s second longest road tunnel, and the longest located outside Europe, which carries the Central Circular Route (C2) of the Shuto Expressway in Tokyo, Japan, from the Takamatsu on-ramp in Toshima to near the ?i Junction in Shinagawa. It has a length of 18.2 kilometers (11.3 mi).
Work on the tunnel began in 1992 but it was completely opened quite recently, in 2015. In the construction of the Yamate Tunnel, innovative technologies such as large section shield tunnel construction method and non open cut method were adopted. This large-section shield tunneling method was mainly used in the construction of the Yamate Tunnel to minimize the effect on traffic in existing roads and to reduce noise and vibration in the surrounding area during construction. The outside diameter of the shield tunnels is 11.2 to 13.0 meters. Lying 30 meters (98 ft) below the surface, about 70 percent of the tunnel was constructed by the tunneling shield method. The tunnel has two lanes in each direction for efficient movement of traffic. Nearly all of the tunnel lies beneath Yamate Dori. On completion in 2015 the Yamate Tunnel surpassed the Kan’etsu Tunnel on the Kan-Etsu Expressway, to become the longest road tunnel in Japan and the second longest in the world.
A tunnel of this scale requires many operational and safety facilities. Among them are fire-safety equipment, that includes infrared sensors, fire extinguishers, foam sprayers, and pushbutton alarms, emergency exits leading to a separate emergency path, that are located no more than 350 meters (1,150 ft) apart and emergency telephones and cameras that are placed at 100-meter (330 ft) intervals. Stairways lead up to Yamate Street. A duct running parallel to the roadway supplies fresh air and removes exhaust. Dust-collection systems are designed to remove 80 percent of particulates from the air.