The airbag system has a sensor (1), a control device (2) and an airbag (3) actuated by the control device when the sensor signal meets given criteria. The sensor provides an acceleration signal which is integrated into a velocity, which is compared with a threshold value before the airbag is released. The threshold value can be varied in dependence on one or more vehicle parameters and as a given function of the time, according to stored values held in a table, or in dependence on the condition of the integrator.
