Sudden natural death while driving has been insufficiently elucidated in Japan owing to the system of voluntary notification of relevant diseases when applying for driver's licenses and the low autopsy rates of traffic accident deaths. This report discusses the behaviors of the vehicles immediately after the drivers' death and the circumstances of the accidents with information obtained from police and the forensic autopsy findings. The results suggested that in a number of cases the cause of death of the driver might be misidentified as injuries resulting from an accident caused by human error such as delayed recognition, misjudgment or mishandling of the vehicle, if autopsy had not been performed. Furthermore, accidents caused by sudden natural death of the driver might be misclassified among fatal accidents in Japanese traffic statistics.

Our results demonstrate the importance of employing information gained from autopsy records in accident analysis to distinguish between fatal accidents and sudden natural death while driving, in order to clarify the degree to which human factors contribute to causing accidents.