The article presents a mathematical model for the study of a passenger coach hunting motion using the multibody approach. The model comprises the lateral displacement, rolling and yawing motions for the main constitutive elements: axles, bogies and case. The equation system is written applying energetic methods. The forced vibrations determined by the irregular profile of the tracks are considered. The wheel -rail contact forces are expressed using the creepage coefficients established

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... to Kalker's linear theory. The equations system is solved through numeric methods using specialized calculus programs. The response of the system -passenger coach on a tangent track, the critical speed and the influence of the constructive characteristics of the coach on its performances are determined.