As the demand for heavier wheel loads and number of load applications continually increases, it is becoming essential in pavement response analysis to properly characterize the nonlinear behavior of pavement geomaterials, i.e., unbound granular materials often used for base/subbase and fine-grained soils for subgrade. This paper describes the recent finite element (FE) modeling research efforts focused on characterizing nonlinear pavement foundation geomaterials and evaluating multiple wheel load interaction effects by comparing superposed single-wheel pavement responses with the full three-dimensional (3D) FE solutions. The typical stress dependent nonlinear resilient response models were successfully programmed in a user material subroutine of the 3D ABAQUS TM FE flexible pavement analysis model. The results from the full 3D nonlinear analyses indicated that errors due to single wheel load superposition may not be negligible, although the differences were mostly on the conservative side. Computed critical pavement responses, including surface displacements, and their locations in a low volume flexible pavement structure were shown to be significantly influenced by multiple wheel loads from single, tandem, and tridem type axle/wheel arrangements.