One of the various active suspensions, which have been shown to have considerable practical potential, is a switchable damper suspension system. However, previous studies of this system have concentrated on the improvements obtainable for certain fixed road roughness, fixed forward speed and fixed vehicle parameters using a quarter vehicle model. This paper is concerned with an analytical study of a four-degrees of freedom vehicle incorporating a passive and a switchable damper suspension system. A half vehicle model of the switchable damper suspension system with adaptive control strategy is developed. The controller provides a set of gains over different operating conditions. The vibrations of the half vehicle are induced by random road inputs at the front and rear wheels. An investigation of the influence of switchable damper suspension system on vehicle ride quality control is performed on this model and compared with the conventional passive suspension.The simulation results in the time domain showed that the switchable damper suspension system with adaptive control is superior compared with conventional passive one. Specifically, the root mean square of vehicle vertical acceleration is reduced by 20 % using switchable damper suspension system with adaptive control. The power dissipation in suspension relative to power consumed in rolling resistance for switchable damper system is discussed.