This paper proposes the bilateral driver model, which simultaneously takes the steering wheel angle and the driver torque into account. By analyzing this bilateral driver model and vehicle system, this paper shows a new design strategy for improving the vehicle stability, while preserving the handling feeling during lane changing. These improvements consist of the calculation of optimal steering gain and the compensation of system delay time, which is comprised of the vehicle delay and the driver delay. The optimal steering gain calculated by the bilateral driver model is slightly higher than those calculated by the conventional angle-control driver model. The vehicle's delay time can be easily compensated using only lead steering; however, to compensate the driver's delay time, the combination of lead steering together with the feedback of steering torque derivative is necessary. For the covering abstract see ITRD E122482.