The problem of incompatibility between different car types has become an important issue in the society. In two-car crashes, the aggressivity to the other vehicles is a factor often mentioned. In this study aggressivity is defined as the influence on injury outcome in the other vehicle due to differences in car structure and mass of the studied vehicle. The study was based on police reported two-car collisions in Sweden. The influence of car mass and structure on driver relative injury risk was for some vehicle categories analyzed with a new developed technique where the influence of mass and structure was separated.

SUVs were found to have 32% higher mass factor and 23% higher structural aggressivity factor than the average value, resulting in a 62% higher total aggressivity factor than the average. MPVs were found to have 3% higher structural aggressivity factor than average, while the mass factor was 28% higher than average, resulting in 32% higher total aggressivity than that of the average car. It was also found that small cars had higher structural aggressivity factor than larger cars among the family car categories. Only small differences in the structural aggressivity factor was found for cars with different year of introduction, while an increase in the mass factor of approximately 10% between 1970 and 1995 was found. Only a small difference in the structural aggressivity factor was found for cars with different Euro NCAP star rating.