Computer simulations are frequently used to investigate vehicle motion in various maneuvers. Although a wide range of maneuvers and types of vehicle motion can presently be simulated by computer, most current vehicle dynamics simulations do not model vehicle behavior once a roadway or roadside barrier is encountered by a vehicle or once vehicle rollover occurs. If the forces generated through such vehicle body and terrain interactions can be accurately modelled, then computer simulation capabilities can be extended to include post-barrier-impact and post-rollover vehicle motion.This paper describes the development of a vehicle-terrain impact model. The terrain is modelled to represent a roadway, either level or sloped, as well as roadside hazards such as curbs, ditches, and guard rails. Rather than using the lumped-mass-spring method or the computationally intensive finite element approach, this method employs massless, three-dimensional, deformable nodes to represent the vehicle body while imposing modest data and computational requirements upon the simulation. A piecewise-linear force-deformation characteristic is used to model node deformations along each displacement direction of each node. Nodes involved in an impact go through loading, unloading, and reloading phases of deformation. In addition to node-deformation forces, node-damping and node-terrain friction forces are considered by the model. The forces arising from the vehicle-terrain impact are transformed into a resultant force and moment at the vehicle mass center and are provided to the simulation for use in determining vehicle motion.Sample simulation runs demonstrating the utility of the vehicle-terrain impact model are presented. The simulations used in these examples are a stand-alone program developed specifically for this research and the Advanced Dynamic Vehicle Simulation (ADVS) although this impact model could be used with virtually any vehicle dynamics simulation.