To forecast a more-suitable future vehicle state.

In an operation processing device 22, an allowable lateral acceleration and an allowable deceleration are calculated from a friction coefficient of a road surface acquired by a road surface μ acquisition device 16. The curvature information of each prescribed spot obtained from a map data base 14 is obtained. A lateral acceleration at a prescribed spot is estimated from the present car speed, and a supposed deceleration corresponding to the lateral acceleration is obtained. The supposed deceleration is defined as a smaller value than an allowable deceleration obtained from a friction circle. An estimated car speed after being decelerated by the supposed deceleration, the lateral acceleration by the estimated car speed, a supposed deceleration corresponding to the lateral acceleration,... are obtained successively on each prescribed spot until the car speed becomes zero. In this case, when the maximum value among the obtained lateral acceleration on each spot exceeds a prescribed threshold, the alarm is sounded from an alarm device 26 or a deceleration control of the vehicle can be executed by a deceleration device 24.