By annual ridership, the New York City Subway is the busiest rapid transit rail system in both the Western Hemisphere and the Western world, as well as the seventh busiest rapid transit rail system in the world; only the metro (subway) systems in Beijing, Shanghai, Seoul, Tokyo, Guangzhou, and Moscow record higher annual ridership.
The city built most of the lines and leased them to the companies.
these now operate as one division called the B Division.
Rebuilding required the suspension of service on that line south of Chambers Street. By March 2002, seven of those stations had reopened.
The rest (except for Cortlandt Street on the IRT Broadway–Seventh Avenue Line) In October 2012, Hurricane Sandy wreaked havoc, flooding several underwater tunnels and other facilities near New York Harbor, as well as trackage over Jamaica Bay.
Ridership continues to increase, and on September 23, 2014, more than 6.1 million people rode the subway system, establishing the highest single-day ridership since ridership was regularly monitored in 1985.
Of the system's 25 services, 22 pass through Manhattan, the exceptions being the G train, the Franklin Avenue Shuttle, and the Rockaway Park Shuttle.Street railways had to be torn up to allow the work.The foundations of tall buildings often ran near the subway construction, and in some cases needed underpinning to ensure stability.Many lines and stations have both express and local services. Normally, the outer two are used for local trains, while the inner one or two are used for express trains.Stations served by express trains are typically major transfer points or destinations.They had to deal with rock formations and ground water, which required pumps.