Evaluation of vehicle impacts may involve the use of computer simulations. While simulation programs with two-dimensional impact models have been used for decades, more recent three-dimensional impact models have been developed. This research compares DyMESH, the three-dimensional vehicle impact model in HVE-SIMON, with full-scale vehicle crash tests involving low-speed rear impacts. Exponent Failure Analysis Associates (Phoenix, Arizona) conducted rear impact research involving two virtually identical 1983 Nissan Pulsar NX 2-door vehicles. One vehicle was stationary, while the second vehicle impacted the rear of the first vehicle in an aligned configuration. Tests were run at impact speeds ranging from 5 to 20 MPH. Tri-axial accelerometers were positioned in both vehicles and vehicle acceleration and velocity responses were recorded. SIMON-DyMESH was used to simulate these impact tests. DyMESH utilizes a mesh shell determined by the three-dimensional geometry of the vehicle. Crush stiffness coefficients used by DyMESH may not directly translate from A and B stiffness values used in two-dimensional impact simulation programs. Therefore, a method for calculating crush stiffness coefficients for use in three-dimensional impact models using barrier crash test data was applied. SIMON-DyMESH simulated acceleration pulses and velocity changes were compared to the crash test data. The effect of adjusting a simulation input parameter related to the coefficient of restitution was evaluated.