Disclosed is a semiconductor device having improved heat dissipation efficiency. Optimized portions will include gates whose design parameters are to be changed, a first analyzed portion includes gates whose delays and edge slews are to be recomputed, and a second analyzed portion includes gates whose ATs and RATs are to be recomputed during optimization. When the rolling angular speed of the vehicle is increased sharply after the rolling angle has reached a fully bumping rolling angle FB while the rolling angular speed was decreased, it is determined that the vehicle is in a state in which the lateral overturning due to a rolling resonance phenomenon is liable to occur, whereby the threshold value line S is moved toward the origin.