Burt Lancaster performed all his own stunts in this movie. Albert Rémy also got into the act by performing the stunt of uncoupling the engine from the paintings train on a real moving train.
Burt Lancaster took a day off during shooting to play golf when the production was about half completed. On the golf course, he stepped in a hole and re-aggravated an old knee injury. In order to incorporate the real injury into the film, John Frankenheimer had Lancaster's character shot in the leg, thus enabling him to limp through the rest of the shooting.
In reality, the museum's paintings were indeed loaded into a train for shipment to Germany, but fortunately the elaborate deception seen in the movie was not really required. The train was merely routed onto a ring railway and circled around and around Paris until the Allies arrived.
John Frankenheimer said of this film, "I wanted all the realism possible. There are no tricks in this film. When trains crash together, they are real trains. There is no substitute for that kind of reality."
The engine that crashes into a derailed engine was moving at nearly sixty miles per hour. The crash was staged in the town of Acquigny, with extensive safety precautions and special insurance. Only one take was possible, and seven cameras were used.