To reduce vehicles speeding on residential streets, school zones, playgrounds or hospital areas, retarders are quiet often used. Although this device is an effective way of restraining vehicles speed it frequently can be a source of inconvenience to users as well. A study of the behavior of the vehicle, particularly its body, is needed. In the present work, we carry out a comparative study of the motions of the center of gravity of the body (pumping and pitching) and the vertical displacements of the centers of the wheels of a vehicle at various speeds, before and after passing through two speed bumps of identical geometries. We first study the behavior of the vehicle passing over two identical speed bumps based on its speed, then the influence of the geometry of the bump on the behavior of the vehicle. The dynamic study of the system is achieved by establishing the equations of motion from Lagrange formalism. The resulting system of equations is solved numerically by the classical Runge-Kutta method (RK4). In a first approach, the pulse is modeled constant around the bump. One general observation is that all generalized coordinates surveyed make an oscillatory motion around their equilibrium position. The results show that above a certain speed, the rear of the vehicle rises a little more than before, which could create a sense of discomfort for passengers.

speed limit, raised pavement, bumps, vehicle vibrations, pumping, pitching.