The morning commuter crush in Brooklyn, the city's most populated borough, can be overwhelming. Tempers can fray. Sometimes commuters have to wait for at least one, if not two trains to go by before they can board.
"I saw two women pulling each other's hair because they had bumped into each other," said commuter Ana Fernandez, although such behaviour is rare.
Kevin Ortiz, spokesman for the Metropolitan Transportation Authority (MTA) that operates the subway, said: "We are a victim of our own success."
The city's population has grown by nearly a million since 1994 and crime in the subway, at an all-time high in the early 1990s, has drastically fallen.
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Since 1981, USD 115 billion has been invested in what is one of the oldest subway networks in the world, which Ortiz described as having been in a "state of decay and disrepair" in the early 1980s.
Today, it is considered the quickest and cheapest mode of transport around the city and operates 24 hours a day, seven days a week.
"Crowding issues are likely a larger source of troubles," he said. "The trains are safe and clean, and breakdowns are rare.