Stiffness has been used to characterize a vehicle’s crash behavior, and how it acts with collision partners and roadside structures. It also plays an important role in restraint design. This paper utilized crash test data from the 1982 to 2001 frontal U.S. New Car Assessment Program to evaluate three methods for computing vehicle stiffness. Test parameters, such as load cell force, dynamic displacement and measured crush, were used to compare stiffness trends in the passenger car fleet. Each method predicted a steady increase in passenger car stiffness.

Force-deflection profiles were averaged and examined historically for each passenger car class. Results were compared against light trucks, vans and sport utility vehicles (LTVs) to maintain fleet perspective. The initial stiffness method was then used to quantify stiffness of each passenger car and LTV class. Within some vehicle classes, there was a wide range of initial stiffness measures for a given test weight.