All new cars sold in the USA since the 2007 model year are required to have advanced airbags. These are systems designed to There are several different kinds of systems out there, but the one thing they all have in common is that they can vary the airbag deployment force based on different variables. These variables can include some or all of the following: crash severity, occupant weight, seat position, and occupant belt use.
The Idea Behind Advanced Airbags
Advanced airbags use one of two ways to protect smaller and more vulnerable occupants; suppression and low-risk deployment. Suppression, which means turning off the airbag entirely, is only used for children in the passenger seat; airbags must deploy for occupants the size of a "5th percentile female" dummy. This dummy is 5' tall and 110 lbs. Manufacturers can choose which strategy to use for smaller occupants, and testing is done using three sizes of child dummy: a 12-month infant in a rear-facing car seat, a 3-year-old, and a 6-year-old. This chart shows which strategy that the model of car uses for each child size.
The vast majority of advanced passenger airbags will shut off for an empty seat or a very light weight (such as an infant in a rear-facing car seat), as denoted by a light, which is typically on the dashboard (placement, of course, varies from model to model). Many will shut off for a 3-year-old size occupant, and some will also shut off for a 6-year-old size occupant. If the seat is empty, the light may not come on but the airbag may still be off.
Testing for low-risk deployment for the driver typically involves putting a 5th percentile female dummy with its body in very close proximity to the airbag (such as if they were slumped over the steering wheel) and setting off the airbag. Testing for the passenger involves placing a child dummy "out of position" (i.e. standing in close proximity to the dash) and firing the airbag under its designed deployment parameters for a child of that size. To pass, the dummies must not experience forces that would be likely to result in severe or fatal injury.
The Force Levels
Most systems can choose between two force levels, but there are systems that can choose between three or more. A term for a system that can choose between two force levels may be called "dual stage". The force split most commonly used is 70/30, meaning the first stage of the airbag has 70% of the charge, the second stage has the remaining 30%. The way these stages are deployed varies, however.
Depending on the make and model, the force levels may include:
-Deploying only the SECOND stage of the airbag (usually 30%) - relatively few cars can do this
-Deploying only the FIRST stage of the airbag (usually 70%) - this is a common "low-level" deployment strategy
-Deploying both stages of the airbag, but at different times (these can be as little as 5 milliseconds apart, and as much as 100+) - this can be used as a "low-level" or "high-level" deployment, depending on model
-Deploying both stages of the airbag simultaneously (a "full-force" deployment) - this is obviously used only as a high-level deployment
How Do They Determine What Force You Get?
Advanced airbag systems will use some combination of some or all of these factors to determine what inflation force the airbag goes off with.
Crash severity is a very common one. The idea is simple: in a crash of moderate severity, the airbag inflates at a lower-level force, whereas in a high-severity crash, the airbag can inflate at full force if all other conditions are met.
Occupant weight: other than suppressing the airbag entirely for children as mentioned above, a passenger airbag can also restrict itself to a low-force deployment for some lighter occupants (usually, children - smaller than the 5th percentile female - who are still large enough to gain some benefit from the airbag if seated properly)
Seat position - if a seat is positioned close to an airbag, for instance for a very short occupant who has to move the driver's seat all the way forward, the airbag may restrict itself to a low-force deployment.
Belt use - if an occupant is not wearing the seat belt, the airbag may be more sensitive (require a lower crash severity to deploy) than if the occupant is wearing a seat belt. This can lead to instances where only one of the airbags deploys for two occupants, if one of the occupants is buckled up and the other isn't. In some advanced airbag equipped vehicles that don't shut off the passenger airbag (e.g. use low-risk deployment only), the passenger airbag may even deploy for the empty seat (which wouldn't have a seat belt fastened) while the driver airbag would not deploy for a belted driver.
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