Road traffic accident prevention and control require a multidisciplinary approach as well as the application of many sciences. One of the most difficult problems in studying road traffic accidents is to identify reliable and meaningful information. One possibility to study traffic accidents with and without personal injuries is to use the reports from an insurance company. Folksam, the largest motor insurance company in Sweden, has during the last decade systematically studied traffic accidents.

By studying all accidents during one year a lot of information has been obtained.

The injury frequency increases from 1.5 to 3.0% when the service weight of the car decreases from 1,300 kg to 800 kg. The safety development that private cars have undergone during the last two decades has, however, influenced the injury frequency in a positive way.

In this study the decrease in injury frequency due to seat belt use is shown as well as the redistribution of injuries. The main decrease is concentrated to head injuries which decrease is due to seat belt use among front seat occupants.

An unbelted rear seat passenger has a higher injury severity than an unbelted front seat passenger and it is shown that an unbelted rear seat passenger is a considerable risk for the front seat occupant.