Joseph Barbera, of Hanna-Barbera cartoons fame, had an idea to make a movie about ambulance driving. Twentieth Century Fox gave him development money to deliver a script. Barbera heard that screenwriter
Tom Mankiewicz, who'd written several James Bond movies, was interested, and hired him. Barbera set up Mankiewicz with a local ambulance company for some "real world" experience. Mankiewicz rode in an ambulance driven by Tom "Hap" Hazard, and witnessed the results of a stabbing on the Sunset Strip, as well as potential suicide and heart attack victims. After these ride-alongs, Mankiewicz know he had the makings of a terrific movie, and wrote the original script for this movie.
