Perhaps the most alarming factor is an issue at the heart of any discussion about expanding transit systems in U.S. cities: The mostly unexplained and unstudied construction cost premium for transportation projects, and especially underground rail tunnels.
Hong Kong has very high construction costs by the standards of other dense, wealthy cities, with one small subway tunnel costing the equivalent of almost $600 million per kilometer, and another longer one clocking in at nearly $700 million per kilometer. These relatively high costs may partly explain why Hong Kong needs to develop land to pay for new rail lines in the first place.
But New York’s costs blow Hong Kong’s out of the water. The first phase of the Second Avenue subway came in at $1.7 billion per kilometer, and the 7 train extension to Hudson Yards, in one of the last empty corners of Manhattan, cost $1.3 billion per kilometer (a number that would have risen closer to the Second Avenue line’s cost if two stations had been built as planned, rather than just one).
Using value capture to pay for subways is hard enough, but it becomes nearly impossible when costs are anywhere from two (in the case of Hong Kong) to five or more (in the case of Paris) times those of New York’s peer cities.