The SHDV (Selective Hydraulic Damping Valve) works as a controlled hydraulic orifice. If leaks inside the SHDV can be taken into account, the SHDV can produce the desired damping rates. On the basis of the test conducted, it can be seen that when the amount of damping is decreased, the ride comfort is improved in the vertical direction. When driving on a paved road, the reduction of vibration level was about 15-20%, and when driving on a field damping was about 30-35%. According to the cab suspension performance test results, the viscous damping rates in selective damping should be chosen to be as low as possible. The decreased amount of damping improves the ride comfort, but at the cost of increased risk of damper bottoming. End-stop impacts caused by the bottoming, are undesirable for suspension system mountings and impacts have undesirable effects on ride quality. The risk of end-stop impacts can be reduced, for example, by use of position-dependent damping. By choosing this position-dependent damping suitably, the viscous damping can be reduced substantially. On a paved road decreasing the damping won't improve ride quality as dramatically as on a field. This is due to the high degree of friction damping. The proportion of the friction damping to viscous damping is high at low vibration levels. The only function of viscous damping is to damp down the sudden acceleration peaks arising from the obstacles. The selective damping has no significant effect in the sidewise direction. Vibrations in the sidewise direction are going to amplify because the cab sits higher than the vehicle chassis. One possibility could be to completely restrict the sidewise movement of the cab to restrain the intensification of vibrations. A way to improve sidewise damping is to separate the vertical and sidewise damping into two independent systems.