This report performs an analysis based on the data for accident involving personal injuries and serious material damage in the North- Rhine/Westphalia State of Germany. This was supplemented by automotive data available at the Federal Road Traffic Agency. The study is confined to accidents occurring after August 1984. The statistical analysis was made using logit models. The first study hypothesis says that different "mass aggressiveness" in accidents involving cars of different weights produces more serious consequences for the driver of the smaller car, and correspondingly less serious consequences for the driver of the larger vehicle. This hypothesis was only confirmed with reservations. According to the second hypothesis, equal "mass aggressiveness" produces approximately the same consequences for car occupants in head-on collisions involving cars of the same weight. However, this was not confirmed. The empirical analysis showed that the seriousness of the consequences for drivers was associated on average and quite significantly with the curb weight of the driver's own car. The mean seriousness of injuries for drivers in cars with a curb weight between 600 and 799 kg is - regardless of the other car's weight - some 2.5 higher than for drivers of cars with a curb weight between 1,200 and 1,599 kg. For the covering abstract of the conference see IRRD 864606.