For active front steering control systems that intervene in driver's operation to assist in the control of the vehicle's motion, the effect of the man-machine interface is much larger than for other conventional control systems. This paper focuses on human factors. The results of analysis regarding control effects and system design concerns are also described. The user benefits of this control system are improved vehicle stability and reduced driving workload. Both theoretical and experimental evaluations are described. Regarding the man-machine interface, the influence of the oversteer characteristic when braking and turning on driver's steering operation, the influence of driver reaction in system failure and steering wheel reaction torque when driving with the actuator are also analyzed.