IntroductionContinuous enhancements have been observed in vehicle performance, with increasing demands for the improvement of running stability by aerodynamic forces. Such improvements are realized by considering every minute change made to the shape of a vehicle, which influences aerodynamic characteristics. However, the understanding of such aerodynamic effects on the running stability cannot be explained appropriately only by analyses based on conventional steady-state aerodynamic forces. This study aims to understand the influence of unsteady aerodynamic forces caused by vehicle motions on the running road input.Studies on vehicle dynamics affected by unsteady aerodynamic forces due to vehicle motions have been gaining increasing attention in the field of automotive technology, and the necessity of considering unsteady aerodynamic characteristics is being analyzed (e.g.,