All scenes in the subway car were filmed in a studio mockup of IRT World's Fair Lo-V #5674. The producers contacted St. Louis Car Co. for original blueprints of the car and painstakingly reproduced it. Lights were mounted along the car exterior and illuminated sequentially to simulate a speed of 30 mph. The NYC Transit Authority refused to grant permission for filming on its property. Subway footage was filmed by concealing the cameras inside bags. Police became suspicious when they heard whirring sounds inside the bags.
The outdoor scenes of the El train were filmed on and around the Bronx section of the Third Ave El, which closed in early 1973 and was torn down shortly after .
The New York Transit Authority denied permission to film even background shots on its property, but the filmmakers shot them anyway. Cinematographer Gerald Hirschfeld and an assistant rode the subway with a hidden camera, and when its sound was noticed, they stopped and came back later to finish the job. Hirschfeld said in an interview that he filmed in black and white in order to get "the most realistic style of photography possible"; test shots were taken in muted color but they were deemed to distract from the desired somber effect.
This movie was Thelma Ritter's second to last before she suddenly died from a heart attack in 1969 just nine days before her sixty-seventh birthday.