The major actions that move a highway vehicle are the forces and moments generated between the tire and ground; hence, the validity of a simulated vehicle test depends on the quality of both the tire model and the characterization of the ground surface. Other actions come from aerodynamic forces and moments that are affected by the relation of the vehicle body to the ground surface. This paper describes how the ground can be characterized to cover features of interest for most vehicle simulation scenarios involving pavements or other rigid surfaces. The 3D surface is built from tabular data related to specified properties of a road surface such as horizontal geometry, design elevation changes related to curves and drainage (i.e., banking of turns, cross-slope, ditches, etc.), elevation changes due to hills and other major grades, and disturbances and unique features such as bumps and holes. Broadband random-type road roughness is also included. The road model is intended to work with data from many sources, including GPS measurements, design data, road roughness profile measurements, 3D laser-scanned terrain topology, and specific scenarios created by engineers. A road axis system is defined for describing vehicle motions relative to an inclined road surface for aerodynamics and applications where engineers are concerned with motions of the vehicle relative to the ground surface. The methods described in this paper are demonstrated using the commercial CarSim® vehicle dynamics simulation package.