There are many riders who drive motorcycles on winding mountain roads and caused single motorcycle traffic accidents on curved roads by lane departure. Driving a motorcycle requires subtle balancing and maneuvering. In this study, in order to clarify the influence of lane departure caused by inadequate driving maneuvers against road alignment, the authors analyzed the required curve initial operation and driving maneuvers in curves depending on the traveling speed using a kinematics simulation for motorcycle dynamics. In addition, it was analyzed how inadequate driving maneuvers for curved roads can easily cause lane departure.
As a result, it shows that the steering maneuvers and the lean of motorcycle body during the curves are highly affected by the vehicle speed, and the required maneuvers increases rapidly with increasing speed. The inadequate maneuver in the curves, especially for the lean of motorcycle body and steering torque, even by 10%, may cause failure to follow the correct driving path, which may lead to lane departure. Furthermore, the results suggest that road alignment with longitudinal slope and superelevation are more susceptible to the effects of variable steering torque factors, and that a slight steering wobble can easily lead to lane departure on Hilly and Mountainous Road (hereinafter called HMR). The verification with traffic accident statistical data, indicated that downhill left curves and uphill right curves are the contributing factors to the higher occurrence of fatal and serious injury motorcycle accidents. Therefore, safety measures for motorcycles need to be strengthened for these situations.