Interacting forces at tire/terrain interface greatly influence the dynamical motion of a terrain vehicle system. Therefore, in the simulation of the dynamical motion of a terrain vehicle system on a computer requires accurate prediction of these forces. Most terrain vehicles are equipped with wide, low pressure terra tires. Planar tire models provide reasonably accurate prediction of interacting forces if the dimensions of the terrain are much greater than the dimensions of the tire and a local symmetry of the terrain exists about the center plane of the wheel. Otherwise, planar models become inadequate. This paper shows how the planar adaptive footprint tire model is extended into a three-dimensional tire model. This three-dimensional tire model was used to predict the interacting forces between a Ohtsu AT 22×11-8 terra tire engaging two differently shaped obstacles in five different configurations. The predicted forces were found to be in reasonably good agreement with the experimentally measured data.