The Gongbei Tunnel, consisting of a two-way highway of six lanes, covers a cross-section area of 345 square meters. It is the world's largest highway tunnel in terms of cross-section area, over 30 meters under the ground. Engineers have used forced thawing technology to artificially unfreeze a main tunnel of the Hong Kong-Zhuhai-Macao Bridge to reduce the risk of ground settlement. The whole construction of the tunnel will finish by late November.