Vehicles with variable steering characteristics have long been studied and compared with those having typical fixed gear ratio steering, and the variable gear ratio properties are reported to have improved maneuverability and stability in high-speed lane changes and on slippery low-friction road surfaces. However, it is not clear how gear ratios should be set for individual vehicle characteristics. Therefore, the present study has investigated a variable steering gear system using body slip angle feedback for the purpose of improved maneuverability and stability in the critical cornering range and upwards, in excess of the critical limit, and into the countersteer range. The results of a driving simulator experiment show that the steering effect improves and maneuverability and stability increase in the critical cornering range and upwards, in excess of the critical limit, and into the countersteer range by applying linear-variable control to the steering ratio from a body slip angle of 5?. This result is seen both in double lane changes, such as in hazard avoidance, and in J-turns with long drifting. Moreover, it shows an improvement in drift controllability through prompt countersteering. Overall, the present system can enhance the driver’s hazard avoidance capability.
 Amano, Y., Doi, S. and Kawaguchi, H. (1999) Improvement in Evasive Maneuver by Active Control of Steering Angle and Torque Characteristics. Transactions of the Society of Automotive Engineers of Japan, 30, 87-92.
 Shimizu, Y., Kawai, T., Yazuriha, J. and Takimoto, S. (1999) Effects and Design of Steering System with Variable Gear-Ratio According to Vehicle Speed and Steering Wheel Angle. Proceedings of Annual Conference of Society of Automotive Engineers of Japan, Yokohama, May 1999, 9-12.
 Nozaki, H. (2005) Effect of Differential Steering Assist on Drift Running Performance. SAE Paper, 2005-01-3472, 1-8.
 Nozaki, H. (2009) Consideration of Steering Method Control based on Driving Situations. SAE Paper, 2009-01-2866, 1-8.
 Nozaki, H., Shimizu, M. and Sakuno, M. (2010) Consideration of Critical Cornering Control Characteristics via Driving Simulator That Imparts Full-Range Drift Cornering Sensations. SAE International Journal of Commercial Vehicles, 2, 256-263.
 Nozaki, H., Makita, M. and Yoshino, T. (2011) Consideration of Steering Control Method Corresponding to Electric Vehicle Age. SAE Paper, 2011-01-2150, 1-6.