In order to ensure higher road safety for road users when joining and leaving highway, traditional metal fence protected junctions, are replaced with run-off areas. During the diploma we analyse if and how different particle size of gravel influence stopping distance of ball when colliding with them. Numerical model to simulate stopping ball, was made in computer software LS-DYNA. Simulations were made on three different gravel grain sizes and with three different initial ball velocity. Based on results we obtain this way, we found that at lower speed particle size influences the ball stopping distance significantly, while the difference decreases with increasing ball speed. Best results were obtained using particles with a diameter of 25 mm.