Researchers examined data from a Japanese traffic database on more than 100,000 injured front-seat occupants in automobile accidents in which there were two or more rear-seat passengers. The investigators found that front-seat occupants who wore a seat belt were nearly five times as likely to die in a car accident if the rear-seat passengers were unbelted. Had rear seatbelts been worn, nearly 80% of deaths of belted front-seat occupants could have been prevented.