JP2503499B

PURPOSE:To lighten the economical burden of a user by suppressing the energizing of the gas generating means of an air bag system and preventing the expansion of an air bag, when no passenger is seated, even if it is detected that an impact force acts onto the vehicle. CONSTITUTION:When it is detected that the shock over a certain value is applied onto a vehicle, an air bag unit ABGU1 mounted on a vehicle seat expands an air bag ABG1 by the urging of a gas generating device ACT1 by the output of a shock sensor system G, and a driver is protected from the shock. In this case, a relay contact point rl1 is interposed in the forestage of the gas generating device ACT. The relay contact point rl1 corresponding to the concerned seat is controlled to be opened and closed by the energizing through a driver Dr1 by a control system having a CPU1 into which the output signal of a driver detection unit 2 for detecting the presence of a driver on the right and left front seats, when it is detected that no driver is present.