Passenger comfort has been paramount in the design of suspension systems of high speed cars. The main
objective of this paper is to reduce the vertical and pitch accelerations of a half car rail model. A rigid half-car
high speed passenger vehicle with 10 degrees of freedom has been modelled to study the vertical and pitch
accelerations. State space mathematical approach is used to model rail input that takes in track vibrations. An
augmented track and the vehicle model is then designed. An active secondary suspension system based on
the Linear Quadratic Gaussian (LQG) optimal control method is designed. Vehicle performances like vertical
and pitch accelerations, front and rear suspension travel and control forces have been studied and compared
with that of a passive system.