In “Gov. Hochul Sees Light at End of NYC’s Long-Abandoned Second Ave. Subway Tunnel During Tour with MTA Chief,” the Transit Costs Project is cited:
Extending the Second Ave. Subway 1.6 miles to Harlem will cost an estimated $6.3 billion, say MTA officials. That’s $3.9 billion per mile, far and away the highest cost of any subway extension project in the history of the world, according to a study by researchers at New York University’s Marron Institute.