A revision of the modeling of restitution properties in the Simulation Model of Automobile Collisions (SMAC) computer program and the introduction of restitution properties in the third version of the Calspan Reconstruction of Accident Speeds on the Highway (CRASH3) program have been proposed by R.R. McHenry (See IRRD 899774). The revised restitution model extends the original CRASH3 program by accounting for vehicle restitution properties, and revises the restitution model of the original SMAC program. The two different force-deflection models used in the original programs are unified into a single force-deflection model. As a result, the revised CRASH3/SMAC would use identical crush stiffness coefficients and restitution constants to describe the crush response characteristics of vehicles. The restitution portion of the new force deflection model has an underlying problem.The new force-deflection model coupled with improperly determined crush stiffness coefficients and restitution constants can create vehicle properties that are not realistic. Set forth in this paper is a method for determining crush stiffness coefficients and restitution constants for the revised CRASH3 and SMAC. Steps are taken to prevent unrealistic modeling of vehicle properties. Finally, this method will provide a means to calculate the coefficients/constants in the absence of comprehensive testing. (A)
Abstract