It’s a rat race at the Long Island Rail Road.

Riders have been dashing through the Long Island Rail Road hub at Jamaica Center in Queens.

Fresh LIRR schedules drawn up for new service to Grand Central Madison on Manhattan’s East Side have been wreaking havoc on the rails since they went into effect Monday.

“They required everybody to give us maybe 90 seconds to climb up these stairs, climb over three tracks, climb down these stairs and get the Hempstead train. So by the time everybody got here, the train was gone and everybody missed their transfer,” said commuter Douglas Friedrich.

Some platforms here got crowded in the evening rush hour, and some trains were standing room only, as the LIRR ran trains with fewer cars than usual.

“They have not had a good experience this week, we recognize that,” LIRR interim president Catherine Rinaldi said Thursday.

The LIRR chief said the MTA overestimated how many riders would use Grand Central Madison when it opened.

“We are looking on a train-by-basis every train every day how long is it, who’s on it how crowded is it and we’re making adjustments to be able to reflect actually what we’re seeing out there,” Rinaldi said.

To deal with sardine can-conditions on trains coming in and out of Penn Station, the MTA is going to add cars on trains on four major branches. Each car can hold an extra hundred riders and most trains will have 10 cars, some will have 12 cars.

“We’ve already started, so there are some that have already happened and we’ll see more next week,” Rinaldi said. “By Monday, it’ll be noticeably different on a number of trains that have been the most crowded through the week.”

It’s been particularly inconvenient for riders who commute from Atlantic Terminal in Brooklyn.

“It’s been horrible, the trains are packed, you can barely get a seat in the mornings,” commuter Deborah Everett said.

Under the new schedules, Atlantic Terminal service is a shuttle, meaning these riders lost their timed transfers across the platform at Jamaica Center, and now make a mad dash to their connecting ride.

“You have to run up and down. You’re at track 6. No, now it’s track 2, no now it’s track 7,” Everett said. “And you’re running all around the place. Your knees are hurting, your head is hurting, and it’s just really terrible.”

Everett says she may just stay away from the LIRR.

“They need to just go back to the way things were, or figure this out quickly because I’m thinking of driving again.”

For commuters going to and from Brooklyn, the LIRR chief said the MTA will lengthen trains, add more trips and have a train with doors open waiting at the platform, which she believes will keep people from running frantically for their next train.