On December 15, the construction of the Second Jiaozhou Bay Tunnel in Qingdao achieved a key milestone: excavation of the shield-driven section of the south-line main tunnel successfully surpassed 3,000 meters, reaching an important target ahead of schedule.

      The tunnel has a total length of 17.48 kilometers, including a 9.95-kilometer undersea section, making it the longest undersea road tunnel currently under construction in the world. Designed for a speed of 80 kilometers per hour, the tunnel will become a core transportation artery connecting Qingdao's main urban area with the West Coast New Area once completed.