This paper presents a parametric study of automated vehicles using the sensitivity theory. A sixth order dynamic model of an axisymmetric vehicle is developed in the state space format to represent its 3 degrees-of-freedom motion in the lateral, yaw and roll modes. Variations of the important parameters of the vehicle are grouped into three separate vectors: with the elements consisting of inertia, stiffness and damping, and geometric-kinematic parameters respectively. The effect of every element of these vectors on the state variables is studied carefully, a comparison being made among the state variables to reveal the relative influence of the parameter-induced variations. This helps better understanding which mode of the system is more affected by changes in particular parameters and the severity in the transient response and in the steady-state response. Then the effects of a particular vector on the performance of the system is studied.