This paper presents an overview of work performed by the National Highway Traffic Safety Administration's (NHTSA) Vehicle Research and Test Center (VRTC) to test, validate, and improve the planned National Advanced Driving Simulator's (NADS) vehicle dynamics simulation. This vehicle dynamics simulation, called NADSdyna, was developed by the University of Iowa's Center for Computer-Aided Design (CCAD) NADSdyna is based upon CCAD's general purpose, real-time, multi-body dynamics software, referred to as the Real-Time Recursive Dynamics (RTRD), supplemented by vehicle dynamics specific submodules VRTC has “beta tested” NADSdyna, making certain that the software both works as computer code and that it correctly models vehicle dynamics. This paper gives an overview of VRTC's beta test work with NADSdyna.The paper explains the methodology used by VRTC to validate NADSdyna. The techniques used to obtain vehicle parameters are discussed Repeated experimental runs were performed at each test condition to generate sufficient data for statistical analyses The processing paths for both experimental test data and simulation predictions are described. The techniques used to compare simulation predictions with experimentally measured data are presented.The paper continues with an overview of the NADSdyna validation work performed for one vehicle, a 1994 Ford Taurus GL. Due to the complexity of this work, only an overview of this work is presented in this paper. Also included an overview of the simulation evaluation work for two other vehicle dynamics simulations, VDANL and VDM RoAD, that was performed using the Ford Taurus data. VRTC's efforts to improve NADSdyna's predicted steering system feel and to advance the state-of-the-art in steering system modeling are summarized.