In order to achieve lower power consumption, a technique of performing display by utilizing only a part of a display area is used. The apparatus and method set a target roll angle of the vehicle based on a rolling state of the vehicle, calculate a total control quantity for achieving the target roll angle, based on a running condition of the vehicle, and control the braking force applied to each wheel of the vehicle, based on the total control quantity. The ultrasound source and the reflecting unit constitute a resonance cavity. The legs are connected to the gate signal generators. For example, the supplementary fuel may be supplied to facilitate starting and warming up a cold engine, or to cool andor slow down an engine operating above a threshold speed.