Although making various technological innovations in their filmmaking, numerous difficulties bogged down the movie's production. During filming with wet roads, several cars lost control to the point that one driver broke his shoulder bone and another nearly careened into the upstairs window of a house. The production team often decided to include unplanned accidents caught on film in the final movie, coming back hours later to shoot before-and-after scenes so that things fit in the final cut. For major accidents that were part of the story-line, the crew constructed a special cannon-like device that could fire gutted cars a considerable distance.