This paper presents an analysis of the results of a series of crash tests conducted by the NHTSA to identify structural parameters contributing to vehicle aggressiveness in frontal collisions between large and small cars. Effects of front structure stiffness, engine mass and engine position were investigated. In addition, an analytical study of car-to-car and car-to-barrier crashes is reported. A lumped parameter car model was used with multiple linear regression analysis to determine the significance of specific vehicle parameters on aggressiveness, and the capabilities of different types of barriers to "measure" that aggressiveness.