Much of the R&D for real-time driving simulation has focused on accurate models for the kinematics and dynamics of vehicles. The fidelity of simulation, however, depends just as much on the dynamics of the forces supporting the vehicles as it does on vehicle's responses to those forces. Accurate models of the surface and surface-tire interactions are key to simulating the dynamics of those forces. This paper summarizes requirements for real-time surface models, and for modeling the surface/tire force interactions with sufficient fidelity to complement advanced vehicle dynamics models. It also describes work completed to date in demonstrating these models. This involves three related developments: 1) models of real surfaces, 2) software tools and algorithms to create and optimize road databases, and 3) models of deflecting and enveloping tire responses.