17.1 Introduction

Driving a car at the physical limit of adhesion between the tires and the road is an extremely difficult task. Most drivers with average skills cannot handle those situations and will lose control of the vehicle. An explanation of this unfortunate situation can be found in the research contribution of Shibahata et al. ^[1] In this paper a new method, the ?-method, is described. It was developed to analyze the influence of the sideslip angle of the vehicle on its maneuverability. One important conclusion of the study is that the sensitivity of the yaw moment on the vehicle with respect to changes in the steering angle decreases rapidly as the slip angle of the vehicle increases. At large vehicle slip angles, variations in the steering angle change the yaw moment very little while the absolute value of the yaw moment is then almost zero. Large slip angles are values at which the ?-slip angle curve of the tire has its maximum. Therefore, on dry surfaces vehicle maneuverability is lost at vehicle slip angle values larger than approximately 10 , whereas on packed snow this value is approximately 4 .

Another reason for the problems normal drivers have in these situations is that their driving experience is limited largely to driving well within the physical limit of adhesion. It has been shown ^[2] that for drivers with average skills the vehicle slip angle value is typically...