In the shooting script, it was written that during the Tyrannosaur's escape, Dr. Ian Malcolm would simply get out of the car and run away, much as Donald Gennaro had done moments before. In fact, this is how Dr. Malcolm behaves in the scene as written in the book. When the time came to film the scene, it was Jeff Goldblum's idea to make his flight more heroic, by having him distract the Tyrannosaur so Dr. Grant could save the children.