Abstract
A simple preview type driver model is combined with the "cornering" bicycle model and vehicle directional stability during high lateral acceleration cornering is discussed over it. Both nonlinearity and first order lag characteristics of tires are considered into the model using the expanded "Magic Formula." The preview time of the driver model is investigated with root locus diagram of the driver-vehicle system to derive optimal value for damping characteristics of the system. Increased tire cornering stiffness and wheelbase reduces system response lag and increases its stability, and make the vehicle have less influence from driver's lag constant or steering gain.