Development of active safety systems of automobiles is nowadays based not only on road tests, but also on computer simulation of vehicle's curvilinear motion. To properly perform simulation, all required model parameters have to be properly estimated. The less complicated model is, the less parameters it requires. So that, it makes no sense to apply too complicated models, if we are not able to estimate parameters with relatively low error. One of the most popular is two- degree-of-freedom flat model to describe curvilinear motion of automobile. It is widely used in design and improvement of active safety systems. The article discusses the application of simple two- degree-of-freedom flat model of automobile, which requires only several parameters. These parameters are: mass of a vehicle, location of center of gravity of a vehicle, yaw mass moment of inertia of a vehicle, side-slip characteristics. Furthermore, to be able to compare simulation and measurement results, it is necessary to know some input signals such as steering wheel angle and velocity of a vehicle, recorded during road tests. In this article signal of steering wheel angle was taken from Controller Area Network (CAN) bus. In case of model of a vehicle, the Authors decided to compare the results of simulation using two different side slip characteristics known as the dependence between lateral reaction force and side slip angle: linear characteristic (constant cornering stiffness) and the characteristic represented by Pacejka’s Magic Formula in steady-state version.