This article studies the decoupling control strategies for a quasi-linearised vehicle model consisting of three degrees of freedom. The key feature of the model is that it preserves strong non-linearities and inherent coupling effects between longitudinal acceleration/braking force, steering angles and state variables of the vehicle, based on which two kinds of decoupling controllers are presented. Firstly, a control law for approximate decoupling of longitudinal, lateral and yaw motions is derived, which requires small control magnitude. Next, by selecting the virtual control inputs, a new input-output map is built, and the input-output decoupling controller is proposed. Furthermore, according to the characteristics of the vehicle model, an exponentially stable observer is designed. Several simulations are included to illustrate the proposed control scheme.