A SEPTA Media/Elwyn Line Regional Rail train going 50 mph slammed into a car that went around lowered signal gates in Upper Darby on Monday, critically injuring the car’s driver.

The driver had followed two other cars that went around the gate at Union Avenue about 9 a.m. after a southbound Media/Elwyn train passed — but while a train headed into the city with 300 passengers bore down on the grade crossing, said Jim Fox, SEPTA’s assistant general manager for system safety.

The engineer applied the brakes, but the train pushed the car more than 500 feet down the tracks before coming to a halt, Fox said.

The woman, who has not been identified, was taken to Penn-Presbyterian Medical Center.

Fox said the accident underscored the need for motorists to heed lowered gates and to not to assume that if a train has gone through a crossing, a second one is not approaching.

“It could have been a lot worse,” Fox said, noting the train could have derailed.