An anterior part of a vehicle is provided with a bumper armature as a structural member having high rigidity. A bumper is disposed front of the bumper armature, and a radiator and an engine are disposed behind the bumper armature. A collision determining device embedded with an acceleration sensor as an airbag development control apparatus is arranged in a position approximately in the center of a vehicle interior. A time period "t" during when a signal waveform curve outputted from the acceleration sensor reaches from a first threshold value to a second threshold value is measured to judge whether or not the time period "t" is equal to or less than a previously set time "s". When t.ltoreq.s satisfied, full development of an airbag in which both of inflators are activated is selected by determining that the collision is occurred under a high speed condition. When t>s is satisfied, depowered development of the airbag in which one of the inflators is activated is selected by determining that the collision is occurred under a non-high speed condition.