Abstract
The history of road accident investigation teams in Finland goes back to 1968, when the activity was started, and since then the teams have been studying the causes behind most of the fatal motor accidents. The case study method applied raised criticism, and a systematic development was started in 1978. This report summarizes that work. The existing activity and its importance were analysed, and the need for development charted. A new methodology was suggested and finally tested in practice. A new case study method is in two parts: reconstruction of the accident and psychological analysis of information flow.