Air bag assembly is inflatable by an inflator mounted on the vehicle forward of the vehicle occupant seat. The air bag assembly has a vertical extending, occupant facing restraining surface located at a distance from the air bag base end. An air bag base wall extends generally horizontally from a base end mounted on the inflator and divides the air bag assembly into a lower air bag portion for restraint of the occupant lower torso and an upper air bag portion for restraint of the upper torso. The upper air bag portion includes an inflatable left hand lobe rising from the left side of the base wall and an inflatable right lobe rising from the right side of the base wall. The left and right hand lobes define an upper un-inflated void space, the lower extent of which is provided by the horizontal extending base wall.