To improve the certainty of a system by measuring an inherent parameter of turning speed under a travelling condition according to different physical methods simultaneously, comparing the obtained parameter values, and recognizing the tilt of a traveling passage directed toward the side.

A turning speed sensor 2, a lateral acceleration sensor 3, a steering angle sensor 4 are mounted on most vehicles 1. An inherent parameter such as turning speed can be directly measured under an identical vehicle condition using these systems and determined based on speed measured through measured lateral acceleration and a steering angle. Only recognition whether the tilt of a travelling passage exists or not is sufficient even through the correct value of the tilt of the travelling passage is not detected in most applications. Therefore, dynamic vehicle control can be recognized whether it operates correctly or not. The easy and prompt detection of the tilt of the travelling passage may be used for activation/inactivation of the complex systems determining the tilting angle correctly.