Deployment of the supplemental restraints depends upon the angle and
severity of an impact. Deployment is not based upon vehicle speed; rather,
deployment is based upon the rate of deceleration as measured by the forces
of gravity (G force) upon the impact sensors. When an impact is severe
enough, the microprocessor in the ACM or the SIACM signals the inflator of
the appropriate airbag units to deploy their airbag cushions. The outboard
front seat belt tensioners are provided with a deployment signal by the ACM
in conjunction with the driver and passenger airbags. During a frontal
vehicle impact, the knee blockers work in concert with properly fastened and
adjusted seat belts to restrain both the driver and the front seat passenger
in the proper position for an airbag deployment. The knee blockers also
absorb and distribute the crash energy from the driver and the front seat
passenger to the structure of the instrument panel. The seat belt tensioner
removes the slack from the outboard front seat belts to provide further
assurance that the driver and front seat passenger are properly positioned
and restrained for an airbag deployment.

Of course, this is for my vehicle, which I tend to keep away from innocent
road signs.

FMB