The world-wide trend of increased urbanization creates problems for expanding and newly-developing cities alike. The increase of population leads to a high amount of demand for reliable infrastructure, nowadays combined with the need for greater energy efficiency and greater public awareness of the environment. Using underground spaces can help cities meet these increased demands while remaining compact or find the space they need to incorporate new functions into an existing city landscape. Underground solutions to urban problems are often considered only if all other options (above ground) are exhausted. When underground solutions are considered and assessed from the planning or initial project stages onwards, more optimal solutions will become attainable. (Sterling, Bobylev: 2016)
Many people assume that we have no room for new roads and that many of the easier ways to enlarge roads have already been implemented. If going out is politically impossible or too costly, one alternative is going down. Freeways completely above ground can lead to early elevated transit lines: torn down and replaced by subsurface or completely underground roads. This already exists in Boston; the underground Central Artery is replacing the elevated John Fitzgerald Expressway. The Gowanus Expressway in Brooklyn, built at the top of the abandoned Third Avenue BMT railway line, is the subject of discussion and controversy as to whether it should be renovated as a highway or torn down and replaced by a tunnel. Such decisions must be taken not only by road, but also by section, through the messy and rough but essential processes of local consultation and discussion. Spectacular examples of inner – city tunnel roads are being built in Europe, Asia and Australia where there are strong objections to the acquisition of land and the construction of surface roads. Major developments in tunneling technology, which have led to significantly lower tunnel construction costs, will make tunnels a more attractive choice in the future. (Samuel:1999)
