Cut out the main section of the train. Score and fold the sides of the train. Shape the rooftop of the train into a curve by pressing the paper against a round pencil or dowel.
Cut out the bottom floor of the train and fold the tabs upwards. Make sure the bottom piece is flat and straight.
Match the 'front' and 'back' ends of the floor and train sides. Then glue the floor section inside the walls of the train, so that the floor is lined up with the bottom of the walls.
Next cut out the ends of the train. Curl the ends by pressing the paper against a round pencil or dowel to match the curved shape of each end of the floor piece. Curl the top of the end piece slightly so that it will match the curvature of the roof of the train car.
Glue the ends of the car to the front and back with the tabs inside.
Cut out the wheels and fold into a small box. Fold the ends of the box to match the angle of the ends of the wheels. Tuck the triangular tabs behind the wheels and glue.
Glue the wheels at the front and back of the train car, in the gray boxes on the bottom of the floor.
At last your model of the IRT train car is finished!