Great summary. For those who want a more detailed and scholarly discussion of this topic, I suggested perusing this paper.It's all about inertia and rate of deceleration. Airbags will deploy when the rate of deceleration reaches a certain threshold determined by accelerometers and crash sensors throughout the vehicle. So in theory you can hit a brick wall at 60 and have no airbag deployment as long as you went through the brick wall and it didn't slow the car enough. The damage on this car at 40 was not that bad indicating an indirect hit that didn't decel the car at a fast enough rate.
(Airbag lesson of the day)
CASE STUDY: AIR BAG NON-DEPLOYMENT
An example of an impact where there was a significant change in velocity, but the driver or front
passenger air bags did not deploy, involved a 2007 Chevrolet Equinox colliding with an
oncoming Harley-Davidson motorcycle. The air bag control module in the Equinox reported a
maximum Delta V of 9.27 mph. This value was within the 8.0 to 14.0 mph range where deployment
(for frontal impact with a solid barrier) is expected; however, the maximum deceleration
recorded for the subject collision was only 3.27 g’s. The deceleration of the Equinox in this
accident was well below the estimated deployment range (7.5 to 13.2 g’s) as shown in Table 3.
Therefore, the driver and passenger air bags rightfully did not deploy.
CASE STUDY: AIR BAG DEPLOYMENT
An example of an impact that did not result in a significant change in velocity, but yet the air bag
deployed, involved a 2007 Chevrolet Corvette that struck several small signs, trees, and a utility
pole off road at a very high rate of speed. As the vehicle struck the first object at over 60 mph,
the air bag control module reported a maximum V of 4.96 mph, which is well below the 8.0 to
14.0 mph range where deployment (for frontal impact with a solid barrier) is expected.
Fortunately, the maximum deceleration recorded at the same time during impact was 11.3 g’s,
which is above the estimated threshold range (6.1 to 10.6 g’s) shown in Table 3. As a result, the
air bags deployed and saved the lives of both the passenger and driver.
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