Three different control algorithms have been applied in autonomous intelligent cruise control system: a PID controller, a Fuzzy logic controller and a sliding mode controller. Autonomous intelligent cruise control systems maintains both the speed and the desired distance to the preceding vehicle. The autonomous intelligent cruise controller is designed to operate under constant headway policy, which means the steady state vehicle spacing is given by the desired headway times vehicle speed. The controller design process and modeling of the vehicle including power train, throttle and brake actuator are described. The computer simulation results for three different control algorithms are compared and evaluated.