Most expensive road tunnel

The “Big Dig” Central Artery/Tunnel Project (CA/T) in Boston, Massachusetts, USA, was constructed between 1991 and 2007 at a cost of US$14.6 billion. It relocated the Interstate 93 and other highways into 3.5 miles (5.6 km) of 8–10-lane tunnels under the city centre and harbour. During the peak construction period (1999–2002), $3 million of work was completed each day by more than 5,000 construction workers. More than 12.2 million m³ of earth was excavated – enough to fill a stadium 16 times over.