Rail vehicle dynamicists Frequently employ roller rigs to study the complex dynamic response of vehicles and trucks. This work presents the analytical and experimental investigation of a one-fifth scale model of a typical North American three-piece Freight truck running on a roller rig. The roller rig was built as part of this research For the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University. Linear and nonlinear mathematical models were also developed to simulate the lateral dynamics of the truck running on the roller rig. The nonlinear model incorporates a lookup table For the wheel/rail geometric constraints, a heuristic creep force model to take into account creep force saturation, and it includes the effects of Coulomb friction in the truck bearings. The linear model predicts the truck's natural Frequency versus speed within 5% of the experimental values. lt also predicts the damping ratio decrease that occurs with increasing truck speed. The nonlinear model simulates the lateral instability known as hunting. The nonlinear model and the roller rig also exhibit small amplitude hunting, in which flange contact does not occur. The nonlinear model simulates the experimentally observed increase in oscillation Frequency that accompanies the onset of flange contact. / Master of Science