The city’s subways are constantly being disrupted — by jerks!

An epidemic of bad behavior by out-of-control passengers has caused the number of delays in the city subway system to skyrocket, according to data obtained by The Post.

The system has degenerated into such a cesspool of trouble-making that more than 2,300 train delays attributed to unruly customers were reported in January — an 80 percent increase over the year before.

The numbers were also up 43 percent in December and 53 percent in November.

The rampant rudeness includes everything from vagrants getting into fistfights to people pulling the emergency brakes — and break dancers causing delays by holding doors open, sources said.

Police are called to many of these incidents, typically by transit workers.

The 6 line had the most delays caused by unruly riders, followed by the 2, 5, E and R, sources said. The 7 and the L were the calmest.

“People think they can do whatever they want,” said a police source. “Smoke, act unruly, start fights. But they don’t realize that they are on MTA property and . . . they don’t realize they have to follow the rules.”

Everyone seemed to have horror stories of trains being held up by thoughtless passengers.

Music teacher Chris Bates, 22, of Washington Heights, said an A train was recently delayed as three drunken men brawled.

“They were trying to punch each other through the doors,” he said. “It was annoying because the train was held up.”

Laura Simpson, 49, of Inwood, said she was disgusted recently when the doors couldn’t close because an adult rider was punching a teenage girl.

“The woman said that somebody pushed her,” said Simpson. “And so she stood in the door and she was punching the girl. And she pushed the girl off the train, and the girl tried to get back on the train, so she was hitting her.”

On Sunday alone, there were more than 20 incidents.

People are always holding the doors and they try to cram their way in when there’s no room. - Pat Cashin

They included a deranged man who punched a female conductor at the Euclid Avenue station on the A line and a violent man who frightened E riders so much, they called for help on an intercom.

An unruly homeless man also hit the emergency brake on a Q train at Times Square and then fled.

Transit cops also recently nabbed an armed straphanger for threatening passengers.

“Move out of the way, you don’t want me to hurt you,” Pedro Moreno, 53, allegedly snapped at riders Feb. 17 at the Lexington Avenue-59th Street station. Cops found a .25-caliber handgun with one round in the chamber.

“People are awful, and they behave despicably during rush hour,” said frustrated carpenter Pat Cashin, 36, of Woodside.

“People are always holding the doors and they try to cram their way in when there’s no room. That’s what’s causing the delays and the arguments. Hands down, it’s worse than it used to be.”

The delays sometimes have deadly results.

On March 10, service was disrupted when a retired correction officer killed a drunken man in the Borough Hall station following a fight on a 4 train.

Additional reporting by Matt Abrahams, Larry Celona and Kevin Fasick