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A vehicle represents a mechanical system, which consists of bodies interconnected by joints, force elements, constraints and other coupling elements. When a vehicle moves on a roadway, it is excited due to roadway surface irregularities. It results to vibration of the vehicle mainly in the vertical direction. These vertical movements are known as a vertical dynamics of vehicles. The level of vibrations characterized by their frequency and amplitudes considerably effects two main phenomena, i.e. driving safety and ride comfort for passengers. Therefore, it is necessary to investigate and analyse response of vehicles to the vertical excitations. This article is aimed at evaluation and research of driving properties of a vehicle by means of simulation computations. In case of analysing vehicle’s mechanical system using a virtual model, it is necessary to define in a proper way not only parameters of an investigated vehicle, but also parameters of the excitations due to a roadway surface irregularities. In the reality, roadway surface irregularities have a stochastic behaviour. These fact is processed using statistical methods and it results to the power spectral density of the roadway surface irregularities. A presented research is focused on evaluation of selected output quantities of a vehicle, which moves on the road at various speeds and on various road qualities. An evaluated vehicle uses independent front wheels suspension and rigid rear axle. Dynamic analyses and assessment of the resulting parameters are performed in the Simpack mutibody software package. Based on reached results it is obvious, that vertical dynamics of the vehicle is affected by road quality and driving speed.