An endless stream of people funnel onto the platforms. Trains arrive with a wall of humanity already blocking the doorways.

As No. 6 trains pull into the upper level of the station, riders scan for an opening and, if they can, squeeze in for a suffocating ride downtown.

"You can wait four or five subways to get on, and you're just smushed," Cynthia Hallenbeck, the chief financial officer at a nonprofit, said before boarding a train on a recent morning.

The Lexington Avenue line is the most crowded in the system, but subway riders across New York City are finding themselves on platforms and trains that are beyond crowded. L train stations in Brooklyn are routinely overwhelmed. In Queens, No. 7 train riders regularly endure packed conditions.

Subway use, now at nearly 1.8 billion rides a year, has not been this high since 1948, when the fare was a nickel and the Dodgers were still almost a decade away from leaving Brooklyn. Today, train delays are rising, and even a hiccup like a sick passenger or a signal malfunction can inundate stations with passengers.