Beyond the Surface: Why Cities Invest Billions in Subways to Solve Congestion, Climate, and Land Use Crises

Underground construction also offers superior strategic flexibility in routing. While surface lines must follow the existing street grid, tunnel boring machines (TBMs) allow engineers to plot the most direct, efficient path between two major hubs, regardless of the buildings or infrastructure above. This ability to shave minutes off a journey dramatically improves the transit system’s competitiveness against private car travel.